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 $239.72   9.400%   $262.2537   $262.25   $262.25   $262.30  
  Purchase #2 $84.99   7.224%   $91.1297   $91.13   $91.15   $91.10  
  Purchase #3 $11.65   4.766%   $12.2052   $12.21   $12.20   $12.20  
  Purchase #4 $99.81   9.433%   $109.2251   $109.23   $109.25   $109.20  
  Purchase #5 $119.65   8.685%   $130.0416   $130.04   $130.05   $130.00  
  Purchase #6 $124.85   4.742%   $130.7704   $130.77   $130.75   $130.80  
  Purchase #7 $213.54   5.741%   $225.7993   $225.80   $225.80   $225.80  
  7 purchase totals = $894.21       $961.4250   $961.43   $961.45   $961.40