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	$143.52	11.360%	$159.8239	$159.82	$159.80	$159.80
Purchase #2	$51.80	7.263%	$55.5622	$55.56	$55.55	$55.60
Purchase #3	$102.91	6.171%	$109.2606	$109.26	$109.25	$109.30
Purchase #4	$176.32	11.667%	$196.8913	$196.89	$196.90	$196.90
Purchase #5	$20.27	9.103%	$22.1152	$22.12	$22.10	$22.10
Purchase #6	$184.87	4.481%	$193.154	$193.15	$193.15	$193.20
Purchase #7	$150.93	13.256%	$170.9373	$170.94	$170.95	$170.90
7 purchase totals =	$830.62		$907.7445	$907.74	$907.70	$907.80