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 $44.43   5.123%   $46.7061   $46.71   $46.70   $46.70  
  Purchase #2 $149.48   5.667%   $157.951   $157.95   $157.95   $158.00  
  Purchase #3 $226.41   4.415%   $236.406   $236.41   $236.40   $236.40  
  Purchase #4 $8.34   4.761%   $8.7371   $8.74   $8.75   $8.70  
  Purchase #5 $176.74   13.220%   $200.105   $200.11   $200.10   $200.10  
  Purchase #6 $165.56   12.706%   $186.5961   $186.60   $186.60   $186.60  
  Purchase #7 $166.59   6.799%   $177.9165   $177.92   $177.90   $177.90  
  7 purchase totals = $937.55       $1,014.4178   $1,014.44   $1,014.40   $1,014.40