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	$122.37	4.230%	$127.5463	$127.55	$127.55	$127.50
Purchase #2	$74.69	10.592%	$82.6012	$82.60	$82.60	$82.60
Purchase #3	$59.65	7.772%	$64.286	$64.29	$64.30	$64.30
Purchase #4	$11.98	3.694%	$12.4225	$12.42	$12.40	$12.40
Purchase #5	$48.29	4.704%	$50.5616	$50.56	$50.55	$50.60
Purchase #6	$25.56	12.688%	$28.8031	$28.80	$28.80	$28.80
Purchase #7	$33.69	9.342%	$36.8373	$36.84	$36.85	$36.80
7 purchase totals =	$376.23		$403.0580	$403.06	$403.05	$403.00