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	$123.35	3.123%	$127.2022	$127.20	$127.20	$127.20
Purchase #2	$11.35	7.177%	$12.1646	$12.16	$12.15	$12.20
Purchase #3	$111.65	10.673%	$123.5664	$123.57	$123.55	$123.60
Purchase #4	$160.62	13.720%	$182.6571	$182.66	$182.65	$182.70
Purchase #5	$246.83	4.190%	$257.1722	$257.17	$257.15	$257.20
Purchase #6	$39.71	10.196%	$43.7588	$43.76	$43.75	$43.80
Purchase #7	$231.86	10.426%	$256.0337	$256.03	$256.05	$256.00
7 purchase totals =	$925.37		$1,002.5550	$1,002.55	$1,002.50	$1,002.70