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 $70.89   8.485%   $76.905   $76.91   $76.90   $76.90  
  Purchase #2 $87.95   5.783%   $93.0361   $93.04   $93.05   $93.00  
  Purchase #3 $205.77   7.745%   $221.7069   $221.71   $221.70   $221.70  
  Purchase #4 $113.95   11.544%   $127.1044   $127.10   $127.10   $127.10  
  Purchase #5 $148.26   7.601%   $159.5292   $159.53   $159.55   $159.50  
  Purchase #6 $182.70   6.534%   $194.6376   $194.64   $194.65   $194.60  
  Purchase #7 $129.67   8.188%   $140.2874   $140.29   $140.30   $140.30  
  7 purchase totals = $939.19       $1,013.2066   $1,013.22   $1,013.25   $1,013.10