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 $183.91   6.433%   $195.7409   $195.74   $195.75   $195.70  
  Purchase #2 $116.55   13.235%   $131.9754   $131.98   $132.00   $132.00  
  Purchase #3 $161.89   8.265%   $175.2702   $175.27   $175.25   $175.30  
  Purchase #4 $116.28   7.374%   $124.8545   $124.85   $124.85   $124.90  
  Purchase #5 $58.67   3.250%   $60.5768   $60.58   $60.60   $60.60  
  Purchase #6 $199.83   11.166%   $222.143   $222.14   $222.15   $222.10  
  Purchase #7 $115.93   9.476%   $126.9155   $126.92   $126.90   $126.90  
  7 purchase totals = $953.06       $1,037.4763   $1,037.48   $1,037.50   $1,037.50