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 $61.46   5.849%   $65.0548   $65.05   $65.05   $65.10  
  Purchase #2 $9.36   11.400%   $10.427   $10.43   $10.45   $10.40  
  Purchase #3 $9.39   8.248%   $10.1645   $10.16   $10.15   $10.20  
  Purchase #4 $195.55   5.473%   $206.2525   $206.25   $206.25   $206.30  
  Purchase #5 $190.92   10.690%   $211.3293   $211.33   $211.35   $211.30  
  Purchase #6 $224.43   12.186%   $251.779   $251.78   $251.80   $251.80  
  Purchase #7 $160.27   11.765%   $179.1258   $179.13   $179.15   $179.10  
  7 purchase totals = $851.38       $934.1329   $934.13   $934.20   $934.20