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 $60.63   4.814%   $63.5487   $63.55   $63.55   $63.50  
  Purchase #2 $66.64   9.244%   $72.8002   $72.80   $72.80   $72.80  
  Purchase #3 $178.40   7.327%   $191.4714   $191.47   $191.45   $191.50  
  Purchase #4 $212.29   11.614%   $236.9454   $236.95   $236.95   $236.90  
  Purchase #5 $213.35   13.781%   $242.7518   $242.75   $242.75   $242.80  
  Purchase #6 $98.28   5.748%   $103.9291   $103.93   $103.95   $103.90  
  Purchase #7 $216.75   13.602%   $246.2323   $246.23   $246.25   $246.20  
  7 purchase totals = $1,046.34       $1,157.6789   $1,157.68   $1,157.70   $1,157.60