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	$70.74	5.262%	$74.4623	$74.46	$74.45	$74.50
Purchase #2	$77.42	5.284%	$81.5109	$81.51	$81.50	$81.50
Purchase #3	$100.83	10.762%	$111.6813	$111.68	$111.70	$111.70
Purchase #4	$232.79	12.379%	$261.6071	$261.61	$261.60	$261.60
Purchase #5	$171.28	4.698%	$179.3267	$179.33	$179.35	$179.30
Purchase #6	$81.91	9.574%	$89.7521	$89.75	$89.75	$89.80
Purchase #7	$81.29	9.754%	$89.219	$89.22	$89.20	$89.20
7 purchase totals =	$816.26		$887.5594	$887.56	$887.55	$887.60