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 $71.98   5.632%   $76.0339   $76.03   $76.05   $76.00  
  Purchase #2 $200.48   3.167%   $206.8292   $206.83   $206.85   $206.80  
  Purchase #3 $210.64   9.378%   $230.3938   $230.39   $230.40   $230.40  
  Purchase #4 $204.88   4.421%   $213.9377   $213.94   $213.95   $213.90  
  Purchase #5 $239.86   4.297%   $250.1668   $250.17   $250.15   $250.20  
  Purchase #6 $112.37   9.361%   $122.889   $122.89   $122.90   $122.90  
  Purchase #7 $229.66   11.837%   $256.8449   $256.84   $256.85   $256.80  
  7 purchase totals = $1,269.87       $1,357.0953   $1,357.09   $1,357.15   $1,357.00