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 $85.44   13.649%   $97.1017   $97.10   $97.10   $97.10  
  Purchase #2 $105.26   10.203%   $115.9997   $116.00   $116.00   $116.00  
  Purchase #3 $66.83   4.225%   $69.6536   $69.65   $69.65   $69.70  
  Purchase #4 $188.80   4.648%   $197.5754   $197.58   $197.60   $197.60  
  Purchase #5 $88.95   6.371%   $94.617   $94.62   $94.60   $94.60  
  Purchase #6 $183.84   5.578%   $194.0946   $194.09   $194.10   $194.10  
  Purchase #7 $24.32   7.398%   $26.1192   $26.12   $26.10   $26.10  
  7 purchase totals = $743.44       $795.1612   $795.16   $795.15   $795.20