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 $24.59   8.688%   $26.7264   $26.73   $26.75   $26.70  
  Purchase #2 $221.61   6.373%   $235.7332   $235.73   $235.75   $235.70  
  Purchase #3 $78.71   7.362%   $84.5046   $84.50   $84.50   $84.50  
  Purchase #4 $152.37   5.855%   $161.2913   $161.29   $161.30   $161.30  
  Purchase #5 $91.89   12.575%   $103.4452   $103.45   $103.45   $103.40  
  Purchase #6 $243.63   8.249%   $263.727   $263.73   $263.75   $263.70  
  Purchase #7 $189.83   10.135%   $209.0693   $209.07   $209.05   $209.10  
  7 purchase totals = $1,002.63       $1,084.4970   $1,084.50   $1,084.55   $1,084.40