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 $61.49   9.493%   $67.3272   $67.33   $67.35   $67.30  
  Purchase #2 $186.89   8.206%   $202.2262   $202.23   $202.25   $202.20  
  Purchase #3 $240.75   12.748%   $271.4408   $271.44   $271.45   $271.40  
  Purchase #4 $88.95   7.556%   $95.6711   $95.67   $95.65   $95.70  
  Purchase #5 $72.60   7.235%   $77.8526   $77.85   $77.85   $77.90  
  Purchase #6 $206.92   7.251%   $221.9238   $221.92   $221.90   $221.90  
  Purchase #7 $97.58   10.271%   $107.6024   $107.60   $107.60   $107.60  
  7 purchase totals = $955.18       $1,044.0441   $1,044.04   $1,044.05   $1,044.00