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 $113.95   4.654%   $119.2532   $119.25   $119.25   $119.30  
  Purchase #2 $173.87   6.335%   $184.8847   $184.88   $184.90   $184.90  
  Purchase #3 $213.89   3.333%   $221.019   $221.02   $221.00   $221.00  
  Purchase #4 $84.49   3.561%   $87.4987   $87.50   $87.50   $87.50  
  Purchase #5 $224.63   9.789%   $246.619   $246.62   $246.60   $246.60  
  Purchase #6 $88.80   5.574%   $93.7497   $93.75   $93.75   $93.70  
  Purchase #7 $65.78   6.464%   $70.032   $70.03   $70.05   $70.00  
  7 purchase totals = $965.41       $1,023.0563   $1,023.05   $1,023.05   $1,023.00