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	$147.69	7.227%	$158.3636	$158.36	$158.35	$158.40
Purchase #2	$51.60	6.164%	$54.7806	$54.78	$54.80	$54.80
Purchase #3	$77.68	9.627%	$85.1583	$85.16	$85.15	$85.20
Purchase #4	$40.49	3.728%	$41.9995	$42.00	$42.00	$42.00
Purchase #5	$78.37	9.332%	$85.6835	$85.68	$85.70	$85.70
Purchase #6	$102.30	9.261%	$111.774	$111.77	$111.75	$111.80
Purchase #7	$127.70	9.537%	$139.8787	$139.88	$139.90	$139.90
7 purchase totals =	$625.83		$677.6382	$677.63	$677.65	$677.80