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 $85.72   10.785%   $94.9649   $94.96   $94.95   $95.00  
  Purchase #2 $156.39   12.622%   $176.1295   $176.13   $176.15   $176.10  
  Purchase #3 $9.51   3.127%   $9.8074   $9.81   $9.80   $9.80  
  Purchase #4 $107.29   10.198%   $118.2314   $118.23   $118.25   $118.20  
  Purchase #5 $85.85   11.439%   $95.6704   $95.67   $95.65   $95.70  
  Purchase #6 $136.56   11.636%   $152.4501   $152.45   $152.45   $152.50  
  Purchase #7 $167.73   4.445%   $175.1856   $175.19   $175.20   $175.20  
  7 purchase totals = $749.05       $822.4393   $822.44   $822.45   $822.50