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 $241.63   8.345%   $261.794   $261.79   $261.80   $261.80  
  Purchase #2 $67.34   6.391%   $71.6437   $71.64   $71.65   $71.60  
  Purchase #3 $91.34   5.346%   $96.223   $96.22   $96.20   $96.20  
  Purchase #4 $87.63   9.668%   $96.1021   $96.10   $96.10   $96.10  
  Purchase #5 $172.34   13.398%   $195.4301   $195.43   $195.45   $195.40  
  Purchase #6 $158.86   3.187%   $163.9229   $163.92   $163.90   $163.90  
  Purchase #7 $131.98   12.194%   $148.0736   $148.07   $148.05   $148.10  
  7 purchase totals = $951.12       $1,033.1894   $1,033.17   $1,033.15   $1,033.10