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 $69.86   8.770%   $75.9867   $75.99   $76.00   $76.00  
  Purchase #2 $106.73   3.826%   $110.8135   $110.81   $110.80   $110.80  
  Purchase #3 $151.45   11.566%   $168.9667   $168.97   $168.95   $169.00  
  Purchase #4 $199.32   3.788%   $206.8702   $206.87   $206.85   $206.90  
  Purchase #5 $213.60   13.358%   $242.1327   $242.13   $242.15   $242.10  
  Purchase #6 $248.60   11.195%   $276.4308   $276.43   $276.45   $276.40  
  Purchase #7 $136.42   4.654%   $142.769   $142.77   $142.75   $142.80  
  7 purchase totals = $1,125.98       $1,223.9696   $1,223.97   $1,223.95   $1,224.00