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 $180.65   7.536%   $194.2638   $194.26   $194.25   $194.30  
  Purchase #2 $87.48   13.594%   $99.372   $99.37   $99.35   $99.40  
  Purchase #3 $199.88   12.227%   $224.3193   $224.32   $224.30   $224.30  
  Purchase #4 $246.34   3.427%   $254.7821   $254.78   $254.80   $254.80  
  Purchase #5 $96.56   7.709%   $104.0038   $104.00   $104.00   $104.00  
  Purchase #6 $130.91   12.610%   $147.4178   $147.42   $147.40   $147.40  
  Purchase #7 $209.33   13.706%   $238.0208   $238.02   $238.00   $238.00  
  7 purchase totals = $1,151.15       $1,262.1796   $1,262.17   $1,262.10   $1,262.20