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	$131.74	11.435%	$146.8045	$146.80	$146.80	$146.80
Purchase #2	$214.33	11.362%	$238.6822	$238.68	$238.70	$238.70
Purchase #3	$93.60	7.401%	$100.5273	$100.53	$100.55	$100.50
Purchase #4	$247.49	12.553%	$278.5574	$278.56	$278.55	$278.60
Purchase #5	$172.33	7.613%	$185.4495	$185.45	$185.45	$185.40
Purchase #6	$5.91	5.635%	$6.243	$6.24	$6.25	$6.20
Purchase #7	$173.71	9.598%	$190.3827	$190.38	$190.40	$190.40
7 purchase totals =	$1,039.11		$1,146.6466	$1,146.64	$1,146.70	$1,146.60