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	$106.58	9.534%	$116.7413	$116.74	$116.75	$116.70
Purchase #2	$191.40	4.619%	$200.2408	$200.24	$200.25	$200.20
Purchase #3	$71.57	4.555%	$74.83	$74.83	$74.85	$74.80
Purchase #4	$89.28	12.736%	$100.6507	$100.65	$100.65	$100.70
Purchase #5	$109.68	7.432%	$117.8314	$117.83	$117.85	$117.80
Purchase #6	$226.95	12.613%	$255.5752	$255.58	$255.60	$255.60
Purchase #7	$96.96	9.852%	$106.5125	$106.51	$106.50	$106.50
7 purchase totals =	$892.42		$972.3819	$972.38	$972.45	$972.30