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 $174.66   11.636%   $194.9834   $194.98   $195.00   $195.00  
  Purchase #2 $235.83   5.381%   $248.52   $248.52   $248.50   $248.50  
  Purchase #3 $33.36   3.504%   $34.5289   $34.53   $34.55   $34.50  
  Purchase #4 $201.69   12.794%   $227.4942   $227.49   $227.50   $227.50  
  Purchase #5 $157.40   13.130%   $178.0666   $178.07   $178.05   $178.10  
  Purchase #6 $110.65   5.205%   $116.4093   $116.41   $116.40   $116.40  
  Purchase #7 $197.47   3.773%   $204.9205   $204.92   $204.90   $204.90  
  7 purchase totals = $1,111.06       $1,204.9229   $1,204.92   $1,204.90   $1,204.90