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 $88.68   7.680%   $95.4906   $95.49   $95.50   $95.50  
  Purchase #2 $49.45   7.799%   $53.3066   $53.31   $53.30   $53.30  
  Purchase #3 $175.88   6.618%   $187.5197   $187.52   $187.50   $187.50  
  Purchase #4 $48.66   6.196%   $51.675   $51.68   $51.70   $51.70  
  Purchase #5 $126.49   6.839%   $135.1407   $135.14   $135.15   $135.10  
  Purchase #6 $178.59   5.553%   $188.5071   $188.51   $188.50   $188.50  
  Purchase #7 $208.27   13.385%   $236.1469   $236.15   $236.15   $236.10  
  7 purchase totals = $876.02       $947.7866   $947.80   $947.80   $947.70