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 $119.92   4.457%   $125.2648   $125.26   $125.25   $125.30  
  Purchase #2 $224.99   7.144%   $241.0633   $241.06   $241.05   $241.10  
  Purchase #3 $233.37   4.261%   $243.3139   $243.31   $243.30   $243.30  
  Purchase #4 $30.68   3.436%   $31.7342   $31.73   $31.75   $31.70  
  Purchase #5 $30.76   6.192%   $32.6647   $32.66   $32.65   $32.70  
  Purchase #6 $126.48   4.635%   $132.3423   $132.34   $132.35   $132.30  
  Purchase #7 $198.76   11.607%   $221.8301   $221.83   $221.85   $221.80  
  7 purchase totals = $964.96       $1,028.2133   $1,028.19   $1,028.20   $1,028.20