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 $54.59   12.163%   $61.2298   $61.23   $61.25   $61.20  
  Purchase #2 $113.64   12.372%   $127.6995   $127.70   $127.70   $127.70  
  Purchase #3 $185.36   5.818%   $196.1442   $196.14   $196.15   $196.10  
  Purchase #4 $187.98   13.420%   $213.2069   $213.21   $213.20   $213.20  
  Purchase #5 $65.68   8.827%   $71.4776   $71.48   $71.50   $71.50  
  Purchase #6 $97.96   3.644%   $101.5297   $101.53   $101.55   $101.50  
  Purchase #7 $163.26   6.616%   $174.0613   $174.06   $174.05   $174.10  
  7 purchase totals = $868.47       $945.3490   $945.35   $945.40   $945.30