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	$226.28	6.768%	$241.5946	$241.59	$241.60	$241.60
Purchase #2	$119.54	11.343%	$133.0994	$133.10	$133.10	$133.10
Purchase #3	$97.54	10.841%	$108.1143	$108.11	$108.10	$108.10
Purchase #4	$211.87	10.133%	$233.3388	$233.34	$233.35	$233.30
Purchase #5	$59.65	9.121%	$65.0907	$65.09	$65.10	$65.10
Purchase #6	$237.76	10.226%	$262.0733	$262.07	$262.05	$262.10
Purchase #7	$92.67	13.483%	$105.1647	$105.16	$105.15	$105.20
7 purchase totals =	$1,045.31		$1,148.4758	$1,148.46	$1,148.45	$1,148.50