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 $62.33   11.708%   $69.6276   $69.63   $69.65   $69.60  
  Purchase #2 $32.76   4.508%   $34.2368   $34.24   $34.25   $34.20  
  Purchase #3 $179.44   12.737%   $202.2953   $202.30   $202.30   $202.30  
  Purchase #4 $82.85   6.510%   $88.2435   $88.24   $88.25   $88.20  
  Purchase #5 $96.35   13.661%   $109.5124   $109.51   $109.50   $109.50  
  Purchase #6 $209.59   11.347%   $233.3722   $233.37   $233.35   $233.40  
  Purchase #7 $125.57   9.561%   $137.5757   $137.58   $137.60   $137.60  
  7 purchase totals = $788.89       $874.8635   $874.87   $874.90   $874.80