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 $23.91   8.561%   $25.9569   $25.96   $25.95   $26.00  
  Purchase #2 $156.90   9.857%   $172.3656   $172.37   $172.35   $172.40  
  Purchase #3 $159.67   9.817%   $175.3448   $175.34   $175.35   $175.30  
  Purchase #4 $78.74   4.613%   $82.3723   $82.37   $82.35   $82.40  
  Purchase #5 $164.57   6.652%   $175.5172   $175.52   $175.50   $175.50  
  Purchase #6 $195.86   13.698%   $222.6889   $222.69   $222.70   $222.70  
  Purchase #7 $102.46   9.348%   $112.038   $112.04   $112.05   $112.00  
  7 purchase totals = $882.11       $966.2837   $966.29   $966.25   $966.30