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 $45.89   5.143%   $48.2501   $48.25   $48.25   $48.30  
  Purchase #2 $177.66   9.515%   $194.5643   $194.56   $194.55   $194.60  
  Purchase #3 $111.87   4.428%   $116.8236   $116.82   $116.80   $116.80  
  Purchase #4 $107.75   5.209%   $113.3627   $113.36   $113.35   $113.40  
  Purchase #5 $241.70   13.316%   $273.8848   $273.88   $273.90   $273.90  
  Purchase #6 $186.99   3.447%   $193.4355   $193.44   $193.45   $193.40  
  Purchase #7 $193.66   11.317%   $215.5765   $215.58   $215.60   $215.60  
  7 purchase totals = $1,065.52       $1,155.8975   $1,155.89   $1,155.90   $1,156.00