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 $53.35   10.238%   $58.812   $58.81   $58.80   $58.80  
  Purchase #2 $195.93   12.719%   $220.8503   $220.85   $220.85   $220.90  
  Purchase #3 $211.76   12.350%   $237.9124   $237.91   $237.90   $237.90  
  Purchase #4 $58.27   5.400%   $61.4166   $61.42   $61.40   $61.40  
  Purchase #5 $64.92   6.873%   $69.382   $69.38   $69.40   $69.40  
  Purchase #6 $125.26   13.638%   $142.343   $142.34   $142.35   $142.30  
  Purchase #7 $229.30   6.542%   $244.3008   $244.30   $244.30   $244.30  
  7 purchase totals = $938.79       $1,035.0171   $1,035.01   $1,035.00   $1,035.00