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 $157.97   5.692%   $166.9617   $166.96   $166.95   $167.00  
  Purchase #2 $223.53   4.355%   $233.2647   $233.26   $233.25   $233.30  
  Purchase #3 $88.29   8.750%   $96.0154   $96.02   $96.00   $96.00  
  Purchase #4 $83.63   7.151%   $89.6104   $89.61   $89.60   $89.60  
  Purchase #5 $234.95   8.613%   $255.1862   $255.19   $255.20   $255.20  
  Purchase #6 $205.71   6.795%   $219.688   $219.69   $219.70   $219.70  
  Purchase #7 $196.65   9.310%   $214.9581   $214.96   $214.95   $215.00  
  7 purchase totals = $1,190.73       $1,275.6845   $1,275.69   $1,275.65   $1,275.80