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 $180.26   8.133%   $194.9205   $194.92   $194.90   $194.90  
  Purchase #2 $236.63   4.389%   $247.0157   $247.02   $247.00   $247.00  
  Purchase #3 $112.89   7.525%   $121.385   $121.39   $121.40   $121.40  
  Purchase #4 $142.82   10.793%   $158.2346   $158.23   $158.25   $158.20  
  Purchase #5 $204.41   5.112%   $214.8594   $214.86   $214.85   $214.90  
  Purchase #6 $223.37   12.461%   $251.2041   $251.20   $251.20   $251.20  
  Purchase #7 $69.26   9.675%   $75.9609   $75.96   $75.95   $76.00  
  7 purchase totals = $1,169.64       $1,263.5802   $1,263.58   $1,263.55   $1,263.60