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	$42.55	13.723%	$48.3891	$48.39	$48.40	$48.40
Purchase #2	$146.38	7.666%	$157.6015	$157.60	$157.60	$157.60
Purchase #3	$54.40	13.280%	$61.6243	$61.62	$61.60	$61.60
Purchase #4	$127.31	4.592%	$133.1561	$133.16	$133.15	$133.20
Purchase #5	$61.53	5.212%	$64.7369	$64.74	$64.75	$64.70
Purchase #6	$47.31	13.485%	$53.6898	$53.69	$53.70	$53.70
Purchase #7	$243.76	9.793%	$267.6314	$267.63	$267.65	$267.60
7 purchase totals =	$723.24		$786.8291	$786.83	$786.85	$786.80