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 $41.69   5.824%   $44.118   $44.12   $44.10   $44.10  
  Purchase #2 $211.34   9.285%   $230.9629   $230.96   $230.95   $231.00  
  Purchase #3 $105.62   11.409%   $117.6702   $117.67   $117.65   $117.70  
  Purchase #4 $117.83   5.121%   $123.8641   $123.86   $123.85   $123.90  
  Purchase #5 $221.30   12.310%   $248.542   $248.54   $248.55   $248.50  
  Purchase #6 $225.69   9.847%   $247.9137   $247.91   $247.90   $247.90  
  Purchase #7 $223.38   6.136%   $237.0866   $237.09   $237.10   $237.10  
  7 purchase totals = $1,146.85       $1,250.1575   $1,250.15   $1,250.10   $1,250.20