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 $65.76   11.201%   $73.1258   $73.13   $73.15   $73.10  
  Purchase #2 $172.77   11.133%   $192.0045   $192.00   $192.00   $192.00  
  Purchase #3 $50.49   12.441%   $56.7715   $56.77   $56.75   $56.80  
  Purchase #4 $96.72   8.857%   $105.2865   $105.29   $105.30   $105.30  
  Purchase #5 $95.39   11.518%   $106.377   $106.38   $106.40   $106.40  
  Purchase #6 $121.81   9.275%   $133.1079   $133.11   $133.10   $133.10  
  Purchase #7 $112.54   4.207%   $117.2746   $117.27   $117.25   $117.30  
  7 purchase totals = $715.48       $783.9478   $783.95   $783.95   $784.00