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 $94.76   4.188%   $98.7285   $98.73   $98.75   $98.70  
  Purchase #2 $129.79   3.482%   $134.3093   $134.31   $134.30   $134.30  
  Purchase #3 $216.40   11.667%   $241.6474   $241.65   $241.65   $241.60  
  Purchase #4 $104.35   11.771%   $116.633   $116.63   $116.65   $116.60  
  Purchase #5 $216.38   5.708%   $228.731   $228.73   $228.75   $228.70  
  Purchase #6 $199.48   11.436%   $222.2925   $222.29   $222.30   $222.30  
  Purchase #7 $77.26   5.578%   $81.5696   $81.57   $81.55   $81.60  
  7 purchase totals = $1,038.42       $1,123.9113   $1,123.91   $1,123.95   $1,123.80