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 $233.67   5.711%   $247.0149   $247.01   $247.00   $247.00  
  Purchase #2 $236.57   4.233%   $246.584   $246.58   $246.60   $246.60  
  Purchase #3 $217.71   9.522%   $238.4403   $238.44   $238.45   $238.40  
  Purchase #4 $71.30   9.300%   $77.9309   $77.93   $77.95   $77.90  
  Purchase #5 $182.49   11.147%   $202.8322   $202.83   $202.85   $202.80  
  Purchase #6 $249.26   4.606%   $260.7409   $260.74   $260.75   $260.70  
  Purchase #7 $217.85   5.333%   $229.4679   $229.47   $229.45   $229.50  
  7 purchase totals = $1,408.85       $1,503.0111   $1,503.00   $1,503.05   $1,502.90