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 $69.76   9.382%   $76.3049   $76.30   $76.30   $76.30  
  Purchase #2 $182.91   6.230%   $194.3053   $194.31   $194.30   $194.30  
  Purchase #3 $8.33   13.227%   $9.4318   $9.43   $9.45   $9.40  
  Purchase #4 $70.40   10.858%   $78.044   $78.04   $78.05   $78.00  
  Purchase #5 $86.33   9.522%   $94.5503   $94.55   $94.55   $94.60  
  Purchase #6 $34.92   6.867%   $37.318   $37.32   $37.30   $37.30  
  Purchase #7 $247.52   10.113%   $272.5517   $272.55   $272.55   $272.60  
  7 purchase totals = $700.17       $762.5060   $762.50   $762.50   $762.50