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 $53.97   13.728%   $61.379   $61.38   $61.40   $61.40  
  Purchase #2 $56.48   4.799%   $59.1905   $59.19   $59.20   $59.20  
  Purchase #3 $202.78   10.679%   $224.4349   $224.43   $224.45   $224.40  
  Purchase #4 $206.56   9.152%   $225.4644   $225.46   $225.45   $225.50  
  Purchase #5 $89.66   9.236%   $97.941   $97.94   $97.95   $97.90  
  Purchase #6 $8.65   13.207%   $9.7924   $9.79   $9.80   $9.80  
  Purchase #7 $179.95   9.568%   $197.1676   $197.17   $197.15   $197.20  
  7 purchase totals = $798.05       $875.3698   $875.36   $875.40   $875.40