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	$195.90	12.592%	$220.5677	$220.57	$220.55	$220.60
Purchase #2	$54.77	5.444%	$57.7517	$57.75	$57.75	$57.80
Purchase #3	$158.52	10.670%	$175.4341	$175.43	$175.45	$175.40
Purchase #4	$239.76	3.664%	$248.5448	$248.54	$248.55	$248.50
Purchase #5	$173.67	13.103%	$196.426	$196.43	$196.45	$196.40
Purchase #6	$239.76	10.451%	$264.8173	$264.82	$264.80	$264.80
Purchase #7	$28.71	11.643%	$32.0527	$32.05	$32.05	$32.10
7 purchase totals =	$1,091.09		$1,195.5943	$1,195.59	$1,195.60	$1,195.60