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	$42.45	13.117%	$48.0182	$48.02	$48.00	$48.00
Purchase #2	$167.77	3.288%	$173.2863	$173.29	$173.30	$173.30
Purchase #3	$164.54	13.689%	$187.0639	$187.06	$187.05	$187.10
Purchase #4	$250.65	10.443%	$276.8254	$276.83	$276.85	$276.80
Purchase #5	$35.53	6.505%	$37.8412	$37.84	$37.85	$37.80
Purchase #6	$71.62	8.579%	$77.7643	$77.76	$77.75	$77.80
Purchase #7	$103.82	4.695%	$108.6943	$108.69	$108.70	$108.70
7 purchase totals =	$836.38		$909.4936	$909.49	$909.50	$909.50