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 $43.68   5.242%   $45.9697   $45.97   $45.95   $46.00  
  Purchase #2 $24.98   4.461%   $26.0944   $26.09   $26.10   $26.10  
  Purchase #3 $158.92   8.693%   $172.7349   $172.73   $172.75   $172.70  
  Purchase #4 $158.41   12.684%   $178.5027   $178.50   $178.50   $178.50  
  Purchase #5 $208.75   13.219%   $236.3447   $236.34   $236.35   $236.30  
  Purchase #6 $166.38   10.395%   $183.6752   $183.68   $183.70   $183.70  
  Purchase #7 $60.91   7.569%   $65.5203   $65.52   $65.50   $65.50  
  7 purchase totals = $822.03       $908.8419   $908.83   $908.85   $908.80