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 $195.83   6.341%   $208.2476   $208.25   $208.25   $208.20  
  Purchase #2 $185.39   8.205%   $200.6012   $200.60   $200.60   $200.60  
  Purchase #3 $41.90   7.406%   $45.0031   $45.00   $45.00   $45.00  
  Purchase #4 $21.36   5.795%   $22.5978   $22.60   $22.60   $22.60  
  Purchase #5 $27.89   4.427%   $29.1247   $29.12   $29.10   $29.10  
  Purchase #6 $211.30   12.461%   $237.6301   $237.63   $237.65   $237.60  
  Purchase #7 $139.49   8.658%   $151.567   $151.57   $151.55   $151.60  
  7 purchase totals = $823.16       $894.7715   $894.77   $894.75   $894.70