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 $202.63   11.537%   $226.0074   $226.01   $226.00   $226.00  
  Purchase #2 $48.76   11.133%   $54.1885   $54.19   $54.20   $54.20  
  Purchase #3 $148.29   13.719%   $168.6339   $168.63   $168.65   $168.60  
  Purchase #4 $104.67   12.598%   $117.8563   $117.86   $117.85   $117.90  
  Purchase #5 $31.73   3.140%   $32.7263   $32.73   $32.75   $32.70  
  Purchase #6 $72.97   10.690%   $80.7705   $80.77   $80.75   $80.80  
  Purchase #7 $47.83   8.310%   $51.8047   $51.80   $51.80   $51.80  
  7 purchase totals = $656.88       $731.9876   $731.99   $732.00   $732.00