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 $111.95   13.464%   $127.0229   $127.02   $127.00   $127.00  
  Purchase #2 $26.68   9.616%   $29.2455   $29.25   $29.25   $29.20  
  Purchase #3 $96.98   4.310%   $101.1598   $101.16   $101.15   $101.20  
  Purchase #4 $133.68   7.612%   $143.8557   $143.86   $143.85   $143.90  
  Purchase #5 $6.32   9.211%   $6.9021   $6.90   $6.90   $6.90  
  Purchase #6 $208.35   5.691%   $220.2072   $220.21   $220.20   $220.20  
  Purchase #7 $91.50   7.246%   $98.1301   $98.13   $98.15   $98.10  
  7 purchase totals = $675.46       $726.5233   $726.53   $726.50   $726.50