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 $24.59   7.257%   $26.3745   $26.37   $26.35   $26.40  
  Purchase #2 $193.30   10.824%   $214.2228   $214.22   $214.20   $214.20  
  Purchase #3 $152.54   4.342%   $159.1633   $159.16   $159.15   $159.20  
  Purchase #4 $107.35   8.226%   $116.1806   $116.18   $116.20   $116.20  
  Purchase #5 $188.32   8.783%   $204.8601   $204.86   $204.85   $204.90  
  Purchase #6 $83.25   13.140%   $94.1891   $94.19   $94.20   $94.20  
  Purchase #7 $57.68   4.491%   $60.2704   $60.27   $60.25   $60.30  
  7 purchase totals = $807.03       $875.2608   $875.25   $875.20   $875.40