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 $114.81   9.859%   $126.1291   $126.13   $126.15   $126.10  
  Purchase #2 $202.97   13.583%   $230.5394   $230.54   $230.55   $230.50  
  Purchase #3 $68.47   13.619%   $77.7949   $77.79   $77.80   $77.80  
  Purchase #4 $115.32   6.275%   $122.5563   $122.56   $122.55   $122.60  
  Purchase #5 $6.97   13.400%   $7.904   $7.90   $7.90   $7.90  
  Purchase #6 $184.54   6.130%   $195.8523   $195.85   $195.85   $195.90  
  Purchase #7 $104.26   8.250%   $112.8615   $112.86   $112.85   $112.90  
  7 purchase totals = $797.34       $873.6375   $873.63   $873.65   $873.70