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	$146.79	8.531%	$159.3127	$159.31	$159.30	$159.30
Purchase #2	$148.59	6.740%	$158.605	$158.61	$158.60	$158.60
Purchase #3	$191.72	10.424%	$211.7049	$211.70	$211.70	$211.70
Purchase #4	$98.51	7.247%	$105.649	$105.65	$105.65	$105.60
Purchase #5	$166.58	4.217%	$173.6047	$173.60	$173.60	$173.60
Purchase #6	$44.96	7.605%	$48.3792	$48.38	$48.40	$48.40
Purchase #7	$215.88	4.813%	$226.2703	$226.27	$226.25	$226.30
7 purchase totals =	$1,013.03		$1,083.5258	$1,083.52	$1,083.50	$1,083.50