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 $118.94   5.440%   $125.4103   $125.41   $125.40   $125.40  
  Purchase #2 $210.98   10.830%   $233.8291   $233.83   $233.85   $233.80  
  Purchase #3 $21.38   11.677%   $23.8765   $23.88   $23.90   $23.90  
  Purchase #4 $17.64   8.657%   $19.1671   $19.17   $19.15   $19.20  
  Purchase #5 $86.73   5.130%   $91.1792   $91.18   $91.20   $91.20  
  Purchase #6 $206.89   13.411%   $234.636   $234.64   $234.65   $234.60  
  Purchase #7 $31.48   11.753%   $35.1798   $35.18   $35.20   $35.20  
  7 purchase totals = $694.04       $763.2780   $763.29   $763.35   $763.30