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	$130.64	3.636%	$135.3901	$135.39	$135.40	$135.40
Purchase #2	$30.76	3.373%	$31.7975	$31.80	$31.80	$31.80
Purchase #3	$116.46	9.314%	$127.3071	$127.31	$127.30	$127.30
Purchase #4	$146.98	7.577%	$158.1167	$158.12	$158.10	$158.10
Purchase #5	$104.59	6.471%	$111.358	$111.36	$111.35	$111.40
Purchase #6	$159.60	13.831%	$181.6743	$181.67	$181.65	$181.70
Purchase #7	$174.45	10.385%	$192.5666	$192.57	$192.55	$192.60
7 purchase totals =	$863.48		$938.2103	$938.22	$938.15	$938.30