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 $53.54   11.203%   $59.5381   $59.54   $59.55   $59.50  
  Purchase #2 $173.48   6.206%   $184.2462   $184.25   $184.25   $184.20  
  Purchase #3 $187.84   12.661%   $211.6224   $211.62   $211.60   $211.60  
  Purchase #4 $169.44   8.678%   $184.144   $184.14   $184.15   $184.10  
  Purchase #5 $6.56   11.159%   $7.292   $7.29   $7.30   $7.30  
  Purchase #6 $169.71   8.481%   $184.1031   $184.10   $184.10   $184.10  
  Purchase #7 $93.98   11.105%   $104.4165   $104.42   $104.40   $104.40  
  7 purchase totals = $854.55       $935.3623   $935.36   $935.35   $935.20