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 $158.60   5.513%   $167.3436   $167.34   $167.35   $167.30  
  Purchase #2 $103.50   3.129%   $106.7385   $106.74   $106.75   $106.70  
  Purchase #3 $93.47   3.749%   $96.9742   $96.97   $96.95   $97.00  
  Purchase #4 $127.88   11.420%   $142.4839   $142.48   $142.50   $142.50  
  Purchase #5 $174.68   13.239%   $197.8059   $197.81   $197.80   $197.80  
  Purchase #6 $158.56   7.874%   $171.045   $171.05   $171.05   $171.00  
  Purchase #7 $241.98   8.251%   $261.9458   $261.95   $261.95   $261.90  
  7 purchase totals = $1,058.67       $1,144.3369   $1,144.34   $1,144.35   $1,144.20