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 $211.73   10.450%   $233.8558   $233.86   $233.85   $233.90  
  Purchase #2 $248.70   6.696%   $265.353   $265.35   $265.35   $265.40  
  Purchase #3 $229.58   5.534%   $242.285   $242.29   $242.30   $242.30  
  Purchase #4 $232.97   11.386%   $259.496   $259.50   $259.50   $259.50  
  Purchase #5 $206.29   3.853%   $214.2384   $214.24   $214.25   $214.20  
  Purchase #6 $230.25   6.757%   $245.808   $245.81   $245.80   $245.80  
  Purchase #7 $68.85   4.540%   $71.9758   $71.98   $72.00   $72.00  
  7 purchase totals = $1,428.37       $1,533.0120   $1,533.03   $1,533.05   $1,533.10