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	$128.60	12.472%	$144.639	$144.64	$144.65	$144.60
Purchase #2	$233.48	12.808%	$263.3841	$263.38	$263.40	$263.40
Purchase #3	$139.55	3.413%	$144.3128	$144.31	$144.30	$144.30
Purchase #4	$226.38	12.473%	$254.6164	$254.62	$254.60	$254.60
Purchase #5	$141.76	3.852%	$147.2206	$147.22	$147.20	$147.20
Purchase #6	$11.68	9.203%	$12.7549	$12.75	$12.75	$12.80
Purchase #7	$179.77	3.335%	$185.7653	$185.77	$185.75	$185.80
7 purchase totals =	$1,061.22		$1,152.6931	$1,152.69	$1,152.65	$1,152.70