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 $192.83   8.358%   $208.9467   $208.95   $208.95   $208.90  
  Purchase #2 $133.88   13.257%   $151.6285   $151.63   $151.65   $151.60  
  Purchase #3 $32.69   4.460%   $34.148   $34.15   $34.15   $34.10  
  Purchase #4 $178.94   10.384%   $197.5211   $197.52   $197.50   $197.50  
  Purchase #5 $187.55   12.785%   $211.5283   $211.53   $211.55   $211.50  
  Purchase #6 $21.63   3.392%   $22.3637   $22.36   $22.35   $22.40  
  Purchase #7 $199.64   5.404%   $210.4285   $210.43   $210.45   $210.40  
  7 purchase totals = $947.16       $1,036.5648   $1,036.57   $1,036.60   $1,036.40