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 $116.68   7.287%   $125.1825   $125.18   $125.20   $125.20  
  Purchase #2 $130.56   10.103%   $143.7505   $143.75   $143.75   $143.80  
  Purchase #3 $109.93   13.474%   $124.742   $124.74   $124.75   $124.70  
  Purchase #4 $119.77   12.514%   $134.758   $134.76   $134.75   $134.80  
  Purchase #5 $40.80   13.805%   $46.4324   $46.43   $46.45   $46.40  
  Purchase #6 $192.67   6.406%   $205.0124   $205.01   $205.00   $205.00  
  Purchase #7 $203.36   12.612%   $229.0078   $229.01   $229.00   $229.00  
  7 purchase totals = $913.77       $1,008.8856   $1,008.88   $1,008.90   $1,008.90