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 $62.73   7.680%   $67.5477   $67.55   $67.55   $67.50  
  Purchase #2 $93.97   11.270%   $104.5604   $104.56   $104.55   $104.60  
  Purchase #3 $154.76   5.820%   $163.767   $163.77   $163.75   $163.80  
  Purchase #4 $175.29   5.701%   $185.2833   $185.28   $185.30   $185.30  
  Purchase #5 $170.88   9.399%   $186.941   $186.94   $186.95   $186.90  
  Purchase #6 $98.44   5.450%   $103.805   $103.81   $103.80   $103.80  
  Purchase #7 $109.42   7.320%   $117.4295   $117.43   $117.45   $117.40  
  7 purchase totals = $865.49       $929.3339   $929.34   $929.35   $929.30