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 $72.63   5.504%   $76.6276   $76.63   $76.65   $76.60  
  Purchase #2 $90.86   13.812%   $103.4096   $103.41   $103.40   $103.40  
  Purchase #3 $225.77   9.315%   $246.8005   $246.80   $246.80   $246.80  
  Purchase #4 $245.90   11.237%   $273.5318   $273.53   $273.55   $273.50  
  Purchase #5 $234.62   3.373%   $242.5337   $242.53   $242.55   $242.50  
  Purchase #6 $220.89   11.447%   $246.1753   $246.18   $246.20   $246.20  
  Purchase #7 $212.57   11.809%   $237.6724   $237.67   $237.65   $237.70  
  7 purchase totals = $1,303.24       $1,426.7509   $1,426.75   $1,426.80   $1,426.70