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	$53.56	11.231%	$59.5753	$59.58	$59.60	$59.60
Purchase #2	$30.68	8.258%	$33.2136	$33.21	$33.20	$33.20
Purchase #3	$139.71	9.762%	$153.3485	$153.35	$153.35	$153.30
Purchase #4	$163.37	7.548%	$175.7012	$175.70	$175.70	$175.70
Purchase #5	$102.40	10.608%	$113.2626	$113.26	$113.25	$113.30
Purchase #6	$90.29	4.688%	$94.5228	$94.52	$94.50	$94.50
Purchase #7	$105.34	10.693%	$116.604	$116.60	$116.60	$116.60
7 purchase totals =	$685.35		$746.2280	$746.22	$746.20	$746.20