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	$69.60	10.661%	$77.0201	$77.02	$77.00	$77.00
Purchase #2	$17.32	8.647%	$18.8177	$18.82	$18.80	$18.80
Purchase #3	$164.69	5.545%	$173.8221	$173.82	$173.80	$173.80
Purchase #4	$54.83	4.814%	$57.4695	$57.47	$57.45	$57.50
Purchase #5	$62.55	13.694%	$71.1156	$71.12	$71.10	$71.10
Purchase #6	$223.68	13.157%	$253.1096	$253.11	$253.10	$253.10
Purchase #7	$80.97	11.404%	$90.2038	$90.20	$90.20	$90.20
7 purchase totals =	$673.64		$741.5584	$741.56	$741.45	$741.50