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	$58.55	6.784%	$62.522	$62.52	$62.50	$62.50
Purchase #2	$170.91	4.231%	$178.1412	$178.14	$178.15	$178.10
Purchase #3	$114.73	11.183%	$127.5603	$127.56	$127.55	$127.60
Purchase #4	$111.40	13.206%	$126.1115	$126.11	$126.10	$126.10
Purchase #5	$147.56	3.698%	$153.0168	$153.02	$153.00	$153.00
Purchase #6	$238.82	6.469%	$254.2693	$254.27	$254.25	$254.30
Purchase #7	$198.30	11.523%	$221.1501	$221.15	$221.15	$221.20
7 purchase totals =	$1,040.27		$1,122.7712	$1,122.77	$1,122.70	$1,122.80