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 $108.71   4.868%   $114.002   $114.00   $114.00   $114.00  
  Purchase #2 $129.75   13.183%   $146.8549   $146.85   $146.85   $146.90  
  Purchase #3 $169.74   3.505%   $175.6894   $175.69   $175.70   $175.70  
  Purchase #4 $108.28   7.342%   $116.2299   $116.23   $116.25   $116.20  
  Purchase #5 $91.79   10.187%   $101.1406   $101.14   $101.15   $101.10  
  Purchase #6 $203.68   5.835%   $215.5647   $215.56   $215.55   $215.60  
  Purchase #7 $126.33   12.235%   $141.7865   $141.79   $141.80   $141.80  
  7 purchase totals = $938.28       $1,011.2680   $1,011.26   $1,011.30   $1,011.30