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 $185.61   8.811%   $201.9641   $201.96   $201.95   $202.00  
  Purchase #2 $133.73   13.299%   $151.5148   $151.51   $151.50   $151.50  
  Purchase #3 $108.69   10.198%   $119.7742   $119.77   $119.75   $119.80  
  Purchase #4 $149.56   3.542%   $154.8574   $154.86   $154.85   $154.90  
  Purchase #5 $119.90   11.353%   $133.5122   $133.51   $133.50   $133.50  
  Purchase #6 $127.73   8.208%   $138.2141   $138.21   $138.20   $138.20  
  Purchase #7 $176.46   12.600%   $198.694   $198.69   $198.70   $198.70  
  7 purchase totals = $1,001.68       $1,098.5308   $1,098.51   $1,098.45   $1,098.60