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 $64.51   11.629%   $72.0119   $72.01   $72.00   $72.00  
  Purchase #2 $94.43   3.328%   $97.5726   $97.57   $97.55   $97.60  
  Purchase #3 $38.59   13.405%   $43.763   $43.76   $43.75   $43.80  
  Purchase #4 $207.52   9.552%   $227.3423   $227.34   $227.35   $227.30  
  Purchase #5 $178.73   4.498%   $186.7693   $186.77   $186.75   $186.80  
  Purchase #6 $100.41   8.547%   $108.992   $108.99   $109.00   $109.00  
  Purchase #7 $194.25   12.128%   $217.8086   $217.81   $217.80   $217.80  
  7 purchase totals = $878.44       $954.2597   $954.25   $954.20   $954.30