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	$85.52	3.643%	$88.6355	$88.64	$88.65	$88.60
Purchase #2	$244.50	7.543%	$262.9426	$262.94	$262.95	$262.90
Purchase #3	$23.60	5.157%	$24.8171	$24.82	$24.80	$24.80
Purchase #4	$66.47	10.250%	$73.2832	$73.28	$73.30	$73.30
Purchase #5	$63.84	11.335%	$71.0763	$71.08	$71.10	$71.10
Purchase #6	$114.29	11.629%	$127.5808	$127.58	$127.60	$127.60
Purchase #7	$45.90	7.104%	$49.1607	$49.16	$49.15	$49.20
7 purchase totals =	$644.12		$697.4962	$697.50	$697.55	$697.50