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 $202.75   5.679%   $214.2642   $214.26   $214.25   $214.30  
  Purchase #2 $86.76   12.658%   $97.7421   $97.74   $97.75   $97.70  
  Purchase #3 $70.62   8.483%   $76.6107   $76.61   $76.60   $76.60  
  Purchase #4 $65.77   4.836%   $68.9506   $68.95   $68.95   $69.00  
  Purchase #5 $42.39   8.697%   $46.0767   $46.08   $46.10   $46.10  
  Purchase #6 $224.99   7.397%   $241.6325   $241.63   $241.65   $241.60  
  Purchase #7 $110.29   7.296%   $118.3368   $118.34   $118.35   $118.30  
  7 purchase totals = $803.57       $863.6136   $863.61   $863.65   $863.60