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 $211.96   6.128%   $224.9489   $224.95   $224.95   $224.90  
  Purchase #2 $213.87   13.162%   $242.0196   $242.02   $242.00   $242.00  
  Purchase #3 $196.77   4.707%   $206.032   $206.03   $206.05   $206.00  
  Purchase #4 $238.50   5.208%   $250.9211   $250.92   $250.90   $250.90  
  Purchase #5 $175.90   6.495%   $187.3247   $187.32   $187.30   $187.30  
  Purchase #6 $58.42   10.127%   $64.3362   $64.34   $64.35   $64.30  
  Purchase #7 $248.66   9.577%   $272.4742   $272.47   $272.45   $272.50  
  7 purchase totals = $1,344.08       $1,448.0567   $1,448.05   $1,448.00   $1,447.90