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	$44.77	8.400%	$48.5307	$48.53	$48.55	$48.50
Purchase #2	$50.86	6.153%	$53.9894	$53.99	$54.00	$54.00
Purchase #3	$55.28	13.253%	$62.6063	$62.61	$62.60	$62.60
Purchase #4	$112.70	13.120%	$127.4862	$127.49	$127.50	$127.50
Purchase #5	$142.79	8.600%	$155.0699	$155.07	$155.05	$155.10
Purchase #6	$216.25	11.689%	$241.5275	$241.53	$241.55	$241.50
Purchase #7	$32.50	9.866%	$35.7065	$35.71	$35.70	$35.70
7 purchase totals =	$655.15		$724.9165	$724.93	$724.95	$724.90