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 $59.95   11.680%   $66.9522   $66.95   $66.95   $67.00  
  Purchase #2 $245.49   3.386%   $253.8023   $253.80   $253.80   $253.80  
  Purchase #3 $201.28   8.775%   $218.9423   $218.94   $218.95   $218.90  
  Purchase #4 $60.84   3.326%   $62.8635   $62.86   $62.85   $62.90  
  Purchase #5 $65.58   10.819%   $72.6751   $72.68   $72.70   $72.70  
  Purchase #6 $215.96   13.110%   $244.2724   $244.27   $244.25   $244.30  
  Purchase #7 $168.98   9.719%   $185.4032   $185.40   $185.40   $185.40  
  7 purchase totals = $1,018.08       $1,104.9110   $1,104.90   $1,104.90   $1,105.00