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 $182.83   6.650%   $194.9882   $194.99   $195.00   $195.00  
  Purchase #2 $195.44   12.189%   $219.2622   $219.26   $219.25   $219.30  
  Purchase #3 $161.73   10.723%   $179.0723   $179.07   $179.05   $179.10  
  Purchase #4 $161.65   9.244%   $176.5929   $176.59   $176.60   $176.60  
  Purchase #5 $96.87   7.600%   $104.2321   $104.23   $104.25   $104.20  
  Purchase #6 $94.99   7.613%   $102.2216   $102.22   $102.20   $102.20  
  Purchase #7 $145.56   12.539%   $163.8118   $163.81   $163.80   $163.80  
  7 purchase totals = $1,039.07       $1,140.1811   $1,140.17   $1,140.15   $1,140.20