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 $84.84   11.604%   $94.6848   $94.68   $94.70   $94.70  
  Purchase #2 $195.87   12.139%   $219.6467   $219.65   $219.65   $219.60  
  Purchase #3 $206.64   4.135%   $215.1846   $215.18   $215.20   $215.20  
  Purchase #4 $103.76   4.706%   $108.6429   $108.64   $108.65   $108.60  
  Purchase #5 $226.39   13.506%   $256.9662   $256.97   $256.95   $257.00  
  Purchase #6 $247.32   5.117%   $259.9754   $259.98   $260.00   $260.00  
  Purchase #7 $249.86   4.707%   $261.6209   $261.62   $261.60   $261.60  
  7 purchase totals = $1,314.68       $1,416.7215   $1,416.72   $1,416.75   $1,416.70