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	$221.40	6.148%	$235.0117	$235.01	$235.00	$235.00
Purchase #2	$117.91	8.152%	$127.522	$127.52	$127.50	$127.50
Purchase #3	$67.85	5.579%	$71.6354	$71.64	$71.65	$71.60
Purchase #4	$108.79	5.312%	$114.5689	$114.57	$114.55	$114.60
Purchase #5	$60.62	8.242%	$65.6163	$65.62	$65.60	$65.60
Purchase #6	$244.63	4.243%	$255.0097	$255.01	$255.00	$255.00
Purchase #7	$214.28	6.523%	$228.2575	$228.26	$228.25	$228.30
7 purchase totals =	$1,035.48		$1,097.6215	$1,097.63	$1,097.55	$1,097.60