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 $58.94   10.457%   $65.1034   $65.10   $65.10   $65.10  
  Purchase #2 $110.63   13.263%   $125.3029   $125.30   $125.30   $125.30  
  Purchase #3 $38.31   8.279%   $41.4817   $41.48   $41.50   $41.50  
  Purchase #4 $126.58   13.447%   $143.6012   $143.60   $143.60   $143.60  
  Purchase #5 $226.36   4.743%   $237.0963   $237.10   $237.10   $237.10  
  Purchase #6 $232.82   11.591%   $259.8062   $259.81   $259.80   $259.80  
  Purchase #7 $74.29   12.297%   $83.4254   $83.43   $83.45   $83.40  
  7 purchase totals = $867.93       $955.8171   $955.82   $955.85   $955.80