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	$134.68	13.689%	$153.1163	$153.12	$153.10	$153.10
Purchase #2	$174.45	13.468%	$197.9449	$197.94	$197.95	$197.90
Purchase #3	$214.33	9.828%	$235.3944	$235.39	$235.40	$235.40
Purchase #4	$233.80	9.448%	$255.8894	$255.89	$255.90	$255.90
Purchase #5	$96.53	9.728%	$105.9204	$105.92	$105.90	$105.90
Purchase #6	$120.94	5.139%	$127.1551	$127.16	$127.15	$127.20
Purchase #7	$32.52	8.503%	$35.2852	$35.29	$35.30	$35.30
7 purchase totals =	$1,007.25		$1,110.7057	$1,110.71	$1,110.70	$1,110.70