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 $203.30   5.292%   $214.0586   $214.06   $214.05   $214.10  
  Purchase #2 $98.89   3.549%   $102.3996   $102.40   $102.40   $102.40  
  Purchase #3 $169.36   4.709%   $177.3352   $177.34   $177.35   $177.30  
  Purchase #4 $185.74   8.543%   $201.6078   $201.61   $201.60   $201.60  
  Purchase #5 $64.68   4.529%   $67.6094   $67.61   $67.60   $67.60  
  Purchase #6 $9.85   13.502%   $11.1799   $11.18   $11.20   $11.20  
  Purchase #7 $68.58   8.339%   $74.2989   $74.30   $74.30   $74.30  
  7 purchase totals = $800.40       $848.4894   $848.50   $848.50   $848.50