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 $68.43   10.601%   $75.6843   $75.68   $75.70   $75.70  
  Purchase #2 $250.95   5.557%   $264.8953   $264.90   $264.90   $264.90  
  Purchase #3 $183.98   6.404%   $195.7621   $195.76   $195.75   $195.80  
  Purchase #4 $244.64   10.638%   $270.6648   $270.66   $270.65   $270.70  
  Purchase #5 $37.43   9.448%   $40.9664   $40.97   $40.95   $41.00  
  Purchase #6 $187.85   8.854%   $204.4822   $204.48   $204.50   $204.50  
  Purchase #7 $122.35   8.659%   $132.9443   $132.94   $132.95   $132.90  
  7 purchase totals = $1,095.63       $1,185.3994   $1,185.39   $1,185.40   $1,185.50