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 $52.46   11.765%   $58.6319   $58.63   $58.65   $58.60  
  Purchase #2 $190.59   13.750%   $216.7961   $216.80   $216.80   $216.80  
  Purchase #3 $180.29   6.266%   $191.587   $191.59   $191.60   $191.60  
  Purchase #4 $85.25   3.139%   $87.926   $87.93   $87.95   $87.90  
  Purchase #5 $191.43   7.686%   $206.1433   $206.14   $206.15   $206.10  
  Purchase #6 $114.83   10.359%   $126.7252   $126.73   $126.75   $126.70  
  Purchase #7 $142.78   10.783%   $158.176   $158.18   $158.20   $158.20  
  7 purchase totals = $957.63       $1,045.9855   $1,046.00   $1,046.10   $1,045.90