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	$215.83	10.569%	$238.6411	$238.64	$238.65	$238.60
Purchase #2	$23.83	5.171%	$25.0622	$25.06	$25.05	$25.10
Purchase #3	$91.66	9.869%	$100.7059	$100.71	$100.70	$100.70
Purchase #4	$118.73	12.609%	$133.7007	$133.70	$133.70	$133.70
Purchase #5	$33.75	5.372%	$35.5631	$35.56	$35.55	$35.60
Purchase #6	$66.73	6.258%	$70.906	$70.91	$70.90	$70.90
Purchase #7	$149.41	4.127%	$155.5762	$155.58	$155.60	$155.60
7 purchase totals =	$699.94		$760.1552	$760.16	$760.15	$760.20