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 $60.89   13.263%   $68.9658   $68.97   $68.95   $69.00  
  Purchase #2 $243.42   12.542%   $273.9497   $273.95   $273.95   $273.90  
  Purchase #3 $244.36   4.265%   $254.782   $254.78   $254.80   $254.80  
  Purchase #4 $32.69   12.336%   $36.7226   $36.72   $36.70   $36.70  
  Purchase #5 $64.67   8.565%   $70.209   $70.21   $70.20   $70.20  
  Purchase #6 $180.43   11.329%   $200.8709   $200.87   $200.85   $200.90  
  Purchase #7 $122.93   5.144%   $129.2535   $129.25   $129.25   $129.30  
  7 purchase totals = $949.39       $1,034.7535   $1,034.75   $1,034.70   $1,034.80