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 $92.44   3.664%   $95.827   $95.83   $95.85   $95.80  
  Purchase #2 $7.67   7.796%   $8.268   $8.27   $8.25   $8.30  
  Purchase #3 $170.71   3.702%   $177.0297   $177.03   $177.05   $177.00  
  Purchase #4 $69.63   3.697%   $72.2042   $72.20   $72.20   $72.20  
  Purchase #5 $162.48   12.805%   $183.2856   $183.29   $183.30   $183.30  
  Purchase #6 $125.97   5.696%   $133.1453   $133.15   $133.15   $133.10  
  Purchase #7 $72.27   7.660%   $77.8059   $77.81   $77.80   $77.80  
  7 purchase totals = $701.17       $747.5657   $747.58   $747.60   $747.50