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 $59.91   4.153%   $62.3981   $62.40   $62.40   $62.40  
  Purchase #2 $192.63   13.247%   $218.1477   $218.15   $218.15   $218.10  
  Purchase #3 $204.30   10.537%   $225.8271   $225.83   $225.85   $225.80  
  Purchase #4 $88.90   8.660%   $96.5987   $96.60   $96.60   $96.60  
  Purchase #5 $104.84   7.764%   $112.9798   $112.98   $113.00   $113.00  
  Purchase #6 $42.34   3.573%   $43.8528   $43.85   $43.85   $43.90  
  Purchase #7 $202.78   11.649%   $226.4018   $226.40   $226.40   $226.40  
  7 purchase totals = $895.70       $986.2060   $986.21   $986.25   $986.20