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	$205.90	10.254%	$227.013	$227.01	$227.00	$227.00
Purchase #2	$101.78	6.249%	$108.1402	$108.14	$108.15	$108.10
Purchase #3	$212.82	5.724%	$225.0018	$225.00	$225.00	$225.00
Purchase #4	$219.62	11.812%	$245.5615	$245.56	$245.55	$245.60
Purchase #5	$241.47	11.240%	$268.6112	$268.61	$268.60	$268.60
Purchase #6	$24.50	4.464%	$25.5937	$25.59	$25.60	$25.60
Purchase #7	$158.31	10.854%	$175.493	$175.49	$175.50	$175.50
7 purchase totals =	$1,164.40		$1,275.4144	$1,275.40	$1,275.40	$1,275.40