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 $60.41   3.705%   $62.6482   $62.65   $62.65   $62.60  
  Purchase #2 $48.81   5.352%   $51.4223   $51.42   $51.40   $51.40  
  Purchase #3 $202.26   9.610%   $221.6972   $221.70   $221.70   $221.70  
  Purchase #4 $152.84   7.584%   $164.4314   $164.43   $164.45   $164.40  
  Purchase #5 $62.63   13.851%   $71.3049   $71.30   $71.30   $71.30  
  Purchase #6 $159.77   9.804%   $175.4339   $175.43   $175.45   $175.40  
  Purchase #7 $231.90   6.744%   $247.5393   $247.54   $247.55   $247.50  
  7 purchase totals = $918.62       $994.4772   $994.47   $994.50   $994.30