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 $61.43   5.413%   $64.7552   $64.76   $64.75   $64.80  
  Purchase #2 $68.58   9.385%   $75.0162   $75.02   $75.00   $75.00  
  Purchase #3 $28.77   3.439%   $29.7594   $29.76   $29.75   $29.80  
  Purchase #4 $108.58   3.607%   $112.4965   $112.50   $112.50   $112.50  
  Purchase #5 $130.57   4.178%   $136.0252   $136.03   $136.05   $136.00  
  Purchase #6 $216.50   6.120%   $229.7498   $229.75   $229.75   $229.70  
  Purchase #7 $236.77   4.387%   $247.1571   $247.16   $247.15   $247.20  
  7 purchase totals = $851.20       $894.9594   $894.98   $894.95   $895.00