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 $86.54   8.808%   $94.1624   $94.16   $94.15   $94.20  
  Purchase #2 $135.36   10.831%   $150.0208   $150.02   $150.00   $150.00  
  Purchase #3 $185.36   5.204%   $195.0061   $195.01   $195.00   $195.00  
  Purchase #4 $250.48   13.614%   $284.5803   $284.58   $284.60   $284.60  
  Purchase #5 $215.31   8.108%   $232.7673   $232.77   $232.75   $232.80  
  Purchase #6 $233.45   10.388%   $257.7008   $257.70   $257.70   $257.70  
  Purchase #7 $236.94   5.376%   $249.6779   $249.68   $249.70   $249.70  
  7 purchase totals = $1,343.44       $1,463.9156   $1,463.92   $1,463.90   $1,464.00