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 $70.78   7.553%   $76.126   $76.13   $76.15   $76.10  
  Purchase #2 $189.56   6.815%   $202.4785   $202.48   $202.50   $202.50  
  Purchase #3 $199.84   7.725%   $215.2776   $215.28   $215.30   $215.30  
  Purchase #4 $203.69   10.334%   $224.7393   $224.74   $224.75   $224.70  
  Purchase #5 $214.31   9.532%   $234.738   $234.74   $234.75   $234.70  
  Purchase #6 $151.91   13.383%   $172.2401   $172.24   $172.25   $172.20  
  Purchase #7 $127.49   8.429%   $138.2361   $138.24   $138.25   $138.20  
  7 purchase totals = $1,157.58       $1,263.8356   $1,263.85   $1,263.95   $1,263.70