Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $101.87   10.573%   $112.6407   $112.64   $112.65   $112.60  
  Purchase #2 $191.87   7.729%   $206.6996   $206.70   $206.70   $206.70  
  Purchase #3 $194.96   13.476%   $221.2328   $221.23   $221.25   $221.20  
  Purchase #4 $239.97   3.518%   $248.4121   $248.41   $248.40   $248.40  
  Purchase #5 $209.79   6.250%   $222.9019   $222.90   $222.90   $222.90  
  Purchase #6 $206.26   11.587%   $230.1593   $230.16   $230.15   $230.20  
  Purchase #7 $162.25   6.332%   $172.5237   $172.52   $172.50   $172.50  
  7 purchase totals = $1,306.97       $1,414.5701   $1,414.56   $1,414.55   $1,414.50