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 $208.58   7.472%   $224.1651   $224.17   $224.15   $224.20  
  Purchase #2 $214.51   12.454%   $241.2251   $241.23   $241.25   $241.20  
  Purchase #3 $94.59   9.537%   $103.611   $103.61   $103.60   $103.60  
  Purchase #4 $176.51   8.190%   $190.9662   $190.97   $190.95   $191.00  
  Purchase #5 $33.25   7.531%   $35.7541   $35.75   $35.75   $35.80  
  Purchase #6 $188.73   8.559%   $204.8834   $204.88   $204.90   $204.90  
  Purchase #7 $202.44   4.607%   $211.7664   $211.77   $211.75   $211.80  
  7 purchase totals = $1,118.61       $1,212.3713   $1,212.38   $1,212.35   $1,212.50