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	$35.31	7.251%	$37.8703	$37.87	$37.85	$37.90
Purchase #2	$105.77	11.596%	$118.0351	$118.04	$118.05	$118.00
Purchase #3	$208.62	5.751%	$220.6177	$220.62	$220.60	$220.60
Purchase #4	$240.38	6.343%	$255.6273	$255.63	$255.65	$255.60
Purchase #5	$107.52	3.372%	$111.1456	$111.15	$111.15	$111.10
Purchase #6	$160.66	5.159%	$168.9484	$168.95	$168.95	$168.90
Purchase #7	$214.31	9.741%	$235.1859	$235.19	$235.20	$235.20
7 purchase totals =	$1,072.57		$1,147.4303	$1,147.45	$1,147.45	$1,147.30