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 $228.27   8.271%   $247.1502   $247.15   $247.15   $247.20  
  Purchase #2 $29.34   8.595%   $31.8618   $31.86   $31.85   $31.90  
  Purchase #3 $213.33   8.397%   $231.2433   $231.24   $231.25   $231.20  
  Purchase #4 $172.48   9.160%   $188.2792   $188.28   $188.30   $188.30  
  Purchase #5 $34.45   6.160%   $36.5721   $36.57   $36.55   $36.60  
  Purchase #6 $184.61   6.148%   $195.9598   $195.96   $195.95   $196.00  
  Purchase #7 $157.75   4.391%   $164.6768   $164.68   $164.70   $164.70  
  7 purchase totals = $1,020.23       $1,095.7432   $1,095.74   $1,095.75   $1,095.90