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	$213.70	8.642%	$232.168	$232.17	$232.15	$232.20
Purchase #2	$55.69	6.109%	$59.0921	$59.09	$59.10	$59.10
Purchase #3	$20.66	9.439%	$22.6101	$22.61	$22.60	$22.60
Purchase #4	$87.66	3.501%	$90.729	$90.73	$90.75	$90.70
Purchase #5	$176.37	5.626%	$186.2926	$186.29	$186.30	$186.30
Purchase #6	$167.93	4.535%	$175.5456	$175.55	$175.55	$175.50
Purchase #7	$103.91	7.517%	$111.7209	$111.72	$111.70	$111.70
7 purchase totals =	$825.92		$878.1583	$878.16	$878.15	$878.10