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	$52.78	3.487%	$54.6204	$54.62	$54.60	$54.60
Purchase #2	$33.78	10.431%	$37.3036	$37.30	$37.30	$37.30
Purchase #3	$156.44	10.265%	$172.4986	$172.50	$172.50	$172.50
Purchase #4	$200.86	5.578%	$212.064	$212.06	$212.05	$212.10
Purchase #5	$208.87	9.284%	$228.2615	$228.26	$228.25	$228.30
Purchase #6	$165.60	5.821%	$175.2396	$175.24	$175.25	$175.20
Purchase #7	$52.49	4.492%	$54.8479	$54.85	$54.85	$54.80
7 purchase totals =	$870.82		$934.8356	$934.83	$934.80	$934.80