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	$242.70	11.751%	$271.2197	$271.22	$271.20	$271.20
Purchase #2	$145.25	4.734%	$152.1261	$152.13	$152.15	$152.10
Purchase #3	$127.38	7.663%	$137.1411	$137.14	$137.15	$137.10
Purchase #4	$144.32	9.492%	$158.0189	$158.02	$158.00	$158.00
Purchase #5	$106.39	5.114%	$111.8308	$111.83	$111.85	$111.80
Purchase #6	$23.59	4.150%	$24.569	$24.57	$24.55	$24.60
Purchase #7	$197.40	9.706%	$216.5596	$216.56	$216.55	$216.60
7 purchase totals =	$987.03		$1,071.4652	$1,071.47	$1,071.45	$1,071.40