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	$244.81	4.858%	$256.7029	$256.70	$256.70	$256.70
Purchase #2	$159.92	9.767%	$175.5394	$175.54	$175.55	$175.50
Purchase #3	$107.79	10.227%	$118.8137	$118.81	$118.80	$118.80
Purchase #4	$171.78	3.685%	$178.1101	$178.11	$178.10	$178.10
Purchase #5	$80.37	10.251%	$88.6087	$88.61	$88.60	$88.60
Purchase #6	$42.75	5.397%	$45.0572	$45.06	$45.05	$45.10
Purchase #7	$207.90	11.276%	$231.3428	$231.34	$231.35	$231.30
7 purchase totals =	$1,015.32		$1,094.1748	$1,094.17	$1,094.15	$1,094.10