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 $72.71   4.527%   $76.0016   $76.00   $76.00   $76.00  
  Purchase #2 $239.71   10.267%   $264.321   $264.32   $264.30   $264.30  
  Purchase #3 $208.99   11.188%   $232.3718   $232.37   $232.35   $232.40  
  Purchase #4 $245.94   3.701%   $255.0422   $255.04   $255.05   $255.00  
  Purchase #5 $128.91   6.804%   $137.681   $137.68   $137.70   $137.70  
  Purchase #6 $237.69   8.429%   $257.7249   $257.72   $257.70   $257.70  
  Purchase #7 $131.75   8.597%   $143.0765   $143.08   $143.10   $143.10  
  7 purchase totals = $1,265.70       $1,366.2190   $1,366.21   $1,366.20   $1,366.20