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 $207.92   8.655%   $225.9155   $225.92   $225.90   $225.90  
  Purchase #2 $39.89   13.625%   $45.325   $45.33   $45.35   $45.30  
  Purchase #3 $16.40   7.679%   $17.6594   $17.66   $17.65   $17.70  
  Purchase #4 $43.55   10.358%   $48.0609   $48.06   $48.05   $48.10  
  Purchase #5 $119.47   5.834%   $126.4399   $126.44   $126.45   $126.40  
  Purchase #6 $84.99   8.709%   $92.3918   $92.39   $92.40   $92.40  
  Purchase #7 $185.63   11.381%   $206.7566   $206.76   $206.75   $206.80  
  7 purchase totals = $697.85       $762.5491   $762.56   $762.55   $762.60