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 $148.63   9.172%   $162.2623   $162.26   $162.25   $162.30  
  Purchase #2 $233.99   12.664%   $263.6225   $263.62   $263.60   $263.60  
  Purchase #3 $227.63   11.278%   $253.3021   $253.30   $253.30   $253.30  
  Purchase #4 $36.63   9.861%   $40.2421   $40.24   $40.25   $40.20  
  Purchase #5 $191.30   9.560%   $209.5883   $209.59   $209.60   $209.60  
  Purchase #6 $173.75   11.545%   $193.8094   $193.81   $193.80   $193.80  
  Purchase #7 $104.84   8.567%   $113.8216   $113.82   $113.80   $113.80  
  7 purchase totals = $1,116.77       $1,236.6483   $1,236.64   $1,236.60   $1,236.60