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	$65.87	10.436%	$72.7442	$72.74	$72.75	$72.70
Purchase #2	$245.72	13.536%	$278.9807	$278.98	$279.00	$279.00
Purchase #3	$42.77	5.673%	$45.1963	$45.20	$45.20	$45.20
Purchase #4	$20.94	5.407%	$22.0722	$22.07	$22.05	$22.10
Purchase #5	$148.53	9.256%	$162.2779	$162.28	$162.30	$162.30
Purchase #6	$203.57	5.821%	$215.4198	$215.42	$215.40	$215.40
Purchase #7	$241.76	13.615%	$274.6756	$274.68	$274.70	$274.70
7 purchase totals =	$969.16		$1,071.3667	$1,071.37	$1,071.40	$1,071.40