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	$130.78	13.275%	$148.141	$148.14	$148.15	$148.10
Purchase #2	$79.31	11.107%	$88.119	$88.12	$88.10	$88.10
Purchase #3	$191.51	10.376%	$211.3811	$211.38	$211.40	$211.40
Purchase #4	$48.31	4.162%	$50.3207	$50.32	$50.30	$50.30
Purchase #5	$113.31	13.363%	$128.4516	$128.45	$128.45	$128.50
Purchase #6	$94.74	7.763%	$102.0947	$102.09	$102.10	$102.10
Purchase #7	$27.58	5.835%	$29.1893	$29.19	$29.20	$29.20
7 purchase totals =	$685.54		$757.6974	$757.69	$757.70	$757.70