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 $34.32   4.107%   $35.7295   $35.73   $35.75   $35.70  
  Purchase #2 $214.45   11.122%   $238.3011   $238.30   $238.30   $238.30  
  Purchase #3 $173.53   9.634%   $190.2479   $190.25   $190.25   $190.20  
  Purchase #4 $194.26   8.200%   $210.1893   $210.19   $210.20   $210.20  
  Purchase #5 $59.27   10.642%   $65.5775   $65.58   $65.60   $65.60  
  Purchase #6 $197.59   8.870%   $215.1162   $215.12   $215.10   $215.10  
  Purchase #7 $191.96   7.311%   $205.9942   $205.99   $206.00   $206.00  
  7 purchase totals = $1,065.38       $1,161.1557   $1,161.16   $1,161.20   $1,161.10