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 $22.58   8.782%   $24.563   $24.56   $24.55   $24.60  
  Purchase #2 $236.54   7.217%   $253.6111   $253.61   $253.60   $253.60  
  Purchase #3 $94.74   7.657%   $101.9942   $101.99   $102.00   $102.00  
  Purchase #4 $239.68   6.782%   $255.9351   $255.94   $255.95   $255.90  
  Purchase #5 $188.58   7.345%   $202.4312   $202.43   $202.45   $202.40  
  Purchase #6 $146.40   5.449%   $154.3773   $154.38   $154.40   $154.40  
  Purchase #7 $64.65   3.457%   $66.885   $66.89   $66.90   $66.90  
  7 purchase totals = $993.17       $1,059.7969   $1,059.80   $1,059.85   $1,059.80