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 $104.82   13.719%   $119.2003   $119.20   $119.20   $119.20  
  Purchase #2 $101.41   4.836%   $106.3142   $106.31   $106.30   $106.30  
  Purchase #3 $87.28   5.450%   $92.0368   $92.04   $92.05   $92.00  
  Purchase #4 $127.97   5.142%   $134.5502   $134.55   $134.55   $134.60  
  Purchase #5 $187.32   3.769%   $194.3801   $194.38   $194.40   $194.40  
  Purchase #6 $10.79   10.539%   $11.9272   $11.93   $11.95   $11.90  
  Purchase #7 $94.97   10.669%   $105.1023   $105.10   $105.10   $105.10  
  7 purchase totals = $714.56       $763.5111   $763.51   $763.55   $763.50