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	$212.54	12.123%	$238.3062	$238.31	$238.30	$238.30
Purchase #2	$71.48	7.587%	$76.9032	$76.90	$76.90	$76.90
Purchase #3	$10.93	9.361%	$11.9532	$11.95	$11.95	$12.00
Purchase #4	$35.53	4.687%	$37.1953	$37.20	$37.20	$37.20
Purchase #5	$18.92	3.178%	$19.5213	$19.52	$19.50	$19.50
Purchase #6	$43.35	6.246%	$46.0576	$46.06	$46.05	$46.10
Purchase #7	$94.92	4.794%	$99.4705	$99.47	$99.45	$99.50
7 purchase totals =	$487.67		$529.4073	$529.41	$529.35	$529.50