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	$106.39	4.818%	$111.5159	$111.52	$111.50	$111.50
Purchase #2	$105.52	10.355%	$116.4466	$116.45	$116.45	$116.40
Purchase #3	$11.36	10.662%	$12.5712	$12.57	$12.55	$12.60
Purchase #4	$77.58	4.556%	$81.1145	$81.11	$81.10	$81.10
Purchase #5	$5.28	9.714%	$5.7929	$5.79	$5.80	$5.80
Purchase #6	$181.51	8.375%	$196.7115	$196.71	$196.70	$196.70
Purchase #7	$26.79	6.345%	$28.4898	$28.49	$28.50	$28.50
7 purchase totals =	$514.43		$552.6424	$552.64	$552.60	$552.60