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 $87.76   8.655%   $95.3556   $95.36   $95.35   $95.40  
  Purchase #2 $183.96   6.135%   $195.2459   $195.25   $195.25   $195.20  
  Purchase #3 $28.81   9.266%   $31.4795   $31.48   $31.50   $31.50  
  Purchase #4 $100.26   5.689%   $105.9638   $105.96   $105.95   $106.00  
  Purchase #5 $204.47   5.254%   $215.2129   $215.21   $215.20   $215.20  
  Purchase #6 $178.90   7.820%   $192.89   $192.89   $192.90   $192.90  
  Purchase #7 $71.65   3.608%   $74.2351   $74.24   $74.25   $74.20  
  7 purchase totals = $855.81       $910.3828   $910.39   $910.40   $910.40