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 $101.27   5.612%   $106.9533   $106.95   $106.95   $107.00  
  Purchase #2 $146.34   3.236%   $151.0756   $151.08   $151.10   $151.10  
  Purchase #3 $183.49   10.170%   $202.1509   $202.15   $202.15   $202.20  
  Purchase #4 $31.48   4.571%   $32.919   $32.92   $32.90   $32.90  
  Purchase #5 $147.65   8.696%   $160.4896   $160.49   $160.50   $160.50  
  Purchase #6 $164.47   13.849%   $187.2475   $187.25   $187.25   $187.20  
  Purchase #7 $233.77   13.541%   $265.4248   $265.42   $265.40   $265.40  
  7 purchase totals = $1,008.47       $1,106.2607   $1,106.26   $1,106.25   $1,106.30