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 $183.96   6.365%   $195.6691   $195.67   $195.65   $195.70  
  Purchase #2 $242.29   7.451%   $260.343   $260.34   $260.35   $260.30  
  Purchase #3 $78.43   9.518%   $85.895   $85.90   $85.90   $85.90  
  Purchase #4 $63.39   8.708%   $68.91   $68.91   $68.90   $68.90  
  Purchase #5 $179.47   13.132%   $203.038   $203.04   $203.05   $203.00  
  Purchase #6 $248.92   7.831%   $268.4129   $268.41   $268.40   $268.40  
  Purchase #7 $97.66   3.382%   $100.9629   $100.96   $100.95   $101.00  
  7 purchase totals = $1,094.12       $1,183.2309   $1,183.23   $1,183.20   $1,183.20