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 $63.95   8.572%   $69.4318   $69.43   $69.45   $69.40  
  Purchase #2 $192.94   5.764%   $204.0611   $204.06   $204.05   $204.10  
  Purchase #3 $196.55   4.430%   $205.2572   $205.26   $205.25   $205.30  
  Purchase #4 $19.63   3.675%   $20.3514   $20.35   $20.35   $20.40  
  Purchase #5 $22.37   6.579%   $23.8417   $23.84   $23.85   $23.80  
  Purchase #6 $229.30   8.140%   $247.965   $247.97   $247.95   $248.00  
  Purchase #7 $84.91   9.813%   $93.2422   $93.24   $93.25   $93.20  
  7 purchase totals = $809.65       $864.1504   $864.15   $864.15   $864.20