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 $191.79   3.152%   $197.8352   $197.84   $197.85   $197.80  
  Purchase #2 $88.41   3.529%   $91.53   $91.53   $91.55   $91.50  
  Purchase #3 $107.53   4.383%   $112.243   $112.24   $112.25   $112.20  
  Purchase #4 $59.97   7.241%   $64.3124   $64.31   $64.30   $64.30  
  Purchase #5 $192.96   11.634%   $215.409   $215.41   $215.40   $215.40  
  Purchase #6 $239.27   8.332%   $259.206   $259.21   $259.20   $259.20  
  Purchase #7 $183.76   10.669%   $203.3654   $203.37   $203.35   $203.40  
  7 purchase totals = $1,063.69       $1,143.9010   $1,143.91   $1,143.90   $1,143.80