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 $84.84   12.723%   $95.6342   $95.63   $95.65   $95.60  
  Purchase #2 $33.68   4.531%   $35.206   $35.21   $35.20   $35.20  
  Purchase #3 $231.83   9.573%   $254.0231   $254.02   $254.00   $254.00  
  Purchase #4 $56.63   6.321%   $60.2096   $60.21   $60.20   $60.20  
  Purchase #5 $237.78   10.509%   $262.7683   $262.77   $262.75   $262.80  
  Purchase #6 $19.44   11.246%   $21.6262   $21.63   $21.65   $21.60  
  Purchase #7 $126.88   3.323%   $131.0962   $131.10   $131.10   $131.10  
  7 purchase totals = $791.08       $860.5636   $860.57   $860.55   $860.50