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 $164.66   10.797%   $182.4383   $182.44   $182.45   $182.40  
  Purchase #2 $141.42   11.580%   $157.7964   $157.80   $157.80   $157.80  
  Purchase #3 $233.28   13.590%   $264.9828   $264.98   $265.00   $265.00  
  Purchase #4 $166.77   12.219%   $187.1476   $187.15   $187.15   $187.10  
  Purchase #5 $99.63   6.357%   $105.9635   $105.96   $105.95   $106.00  
  Purchase #6 $240.27   5.341%   $253.1028   $253.10   $253.10   $253.10  
  Purchase #7 $245.35   11.668%   $273.9774   $273.98   $274.00   $274.00  
  7 purchase totals = $1,291.38       $1,425.4088   $1,425.41   $1,425.45   $1,425.40