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	$207.36	10.138%	$228.3822	$228.38	$228.40	$228.40
Purchase #2	$18.91	9.259%	$20.6609	$20.66	$20.65	$20.70
Purchase #3	$106.71	4.184%	$111.1747	$111.17	$111.15	$111.20
Purchase #4	$142.85	7.680%	$153.8209	$153.82	$153.80	$153.80
Purchase #5	$111.52	12.209%	$125.1355	$125.14	$125.15	$125.10
Purchase #6	$122.44	7.481%	$131.5997	$131.60	$131.60	$131.60
Purchase #7	$238.40	10.804%	$264.1567	$264.16	$264.15	$264.20
7 purchase totals =	$948.19		$1,034.9306	$1,034.93	$1,034.90	$1,035.00