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	$166.38	3.643%	$172.4412	$172.44	$172.45	$172.40
Purchase #2	$218.91	10.694%	$242.3202	$242.32	$242.30	$242.30
Purchase #3	$38.59	9.254%	$42.1611	$42.16	$42.15	$42.20
Purchase #4	$157.78	4.621%	$165.071	$165.07	$165.05	$165.10
Purchase #5	$45.77	3.840%	$47.5276	$47.53	$47.55	$47.50
Purchase #6	$111.52	13.432%	$126.4994	$126.50	$126.50	$126.50
Purchase #7	$73.47	10.794%	$81.4004	$81.40	$81.40	$81.40
7 purchase totals =	$812.42		$877.4209	$877.42	$877.40	$877.40