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 $62.50   11.576%   $69.735   $69.74   $69.75   $69.70  
  Purchase #2 $140.42   7.808%   $151.384   $151.38   $151.40   $151.40  
  Purchase #3 $189.80   6.244%   $201.6511   $201.65   $201.65   $201.70  
  Purchase #4 $181.69   11.290%   $202.2028   $202.20   $202.20   $202.20  
  Purchase #5 $72.81   3.374%   $75.2666   $75.27   $75.25   $75.30  
  Purchase #6 $44.96   11.304%   $50.0423   $50.04   $50.05   $50.00  
  Purchase #7 $32.65   8.398%   $35.3919   $35.39   $35.40   $35.40  
  7 purchase totals = $724.83       $785.6737   $785.67   $785.70   $785.70