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 $84.51   12.582%   $95.143   $95.14   $95.15   $95.10  
  Purchase #2 $226.73   5.777%   $239.8282   $239.83   $239.85   $239.80  
  Purchase #3 $151.46   11.154%   $168.3538   $168.35   $168.35   $168.40  
  Purchase #4 $223.47   9.747%   $245.2516   $245.25   $245.25   $245.30  
  Purchase #5 $187.91   13.431%   $213.1482   $213.15   $213.15   $213.10  
  Purchase #6 $77.80   4.493%   $81.2956   $81.30   $81.30   $81.30  
  Purchase #7 $176.25   13.459%   $199.9715   $199.97   $199.95   $200.00  
  7 purchase totals = $1,128.13       $1,242.9919   $1,242.99   $1,243.00   $1,243.00