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 $97.88   6.739%   $104.4761   $104.48   $104.50   $104.50  
  Purchase #2 $244.54   3.532%   $253.1772   $253.18   $253.20   $253.20  
  Purchase #3 $129.90   8.604%   $141.0766   $141.08   $141.10   $141.10  
  Purchase #4 $48.75   10.546%   $53.8912   $53.89   $53.90   $53.90  
  Purchase #5 $119.75   8.238%   $129.615   $129.62   $129.60   $129.60  
  Purchase #6 $56.36   5.330%   $59.364   $59.36   $59.35   $59.40  
  Purchase #7 $205.68   3.391%   $212.6546   $212.65   $212.65   $212.70  
  7 purchase totals = $902.86       $954.2547   $954.26   $954.30   $954.40