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 $67.48   11.428%   $75.1916   $75.19   $75.20   $75.20  
  Purchase #2 $94.76   7.840%   $102.1892   $102.19   $102.20   $102.20  
  Purchase #3 $71.36   8.251%   $77.2479   $77.25   $77.25   $77.20  
  Purchase #4 $211.30   10.769%   $234.0549   $234.05   $234.05   $234.10  
  Purchase #5 $55.54   13.683%   $63.1395   $63.14   $63.15   $63.10  
  Purchase #6 $103.55   6.193%   $109.9629   $109.96   $109.95   $110.00  
  Purchase #7 $119.96   12.389%   $134.8218   $134.82   $134.80   $134.80  
  7 purchase totals = $723.95       $796.6078   $796.60   $796.60   $796.60