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 $62.34   5.674%   $65.8772   $65.88   $65.90   $65.90  
  Purchase #2 $118.98   3.301%   $122.9075   $122.91   $122.90   $122.90  
  Purchase #3 $169.92   7.134%   $182.0421   $182.04   $182.05   $182.00  
  Purchase #4 $211.45   3.345%   $218.523   $218.52   $218.50   $218.50  
  Purchase #5 $33.42   3.202%   $34.4901   $34.49   $34.50   $34.50  
  Purchase #6 $49.87   7.126%   $53.4237   $53.42   $53.40   $53.40  
  Purchase #7 $166.41   7.332%   $178.6112   $178.61   $178.60   $178.60  
  7 purchase totals = $812.39       $855.8748   $855.87   $855.85   $855.80