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	$43.49	4.201%	$45.317	$45.32	$45.30	$45.30
Purchase #2	$26.71	6.533%	$28.455	$28.46	$28.45	$28.50
Purchase #3	$123.69	5.807%	$130.8727	$130.87	$130.85	$130.90
Purchase #4	$199.94	4.360%	$208.6574	$208.66	$208.65	$208.70
Purchase #5	$107.38	3.852%	$111.5163	$111.52	$111.50	$111.50
Purchase #6	$159.47	13.761%	$181.4147	$181.41	$181.40	$181.40
Purchase #7	$28.62	10.410%	$31.5993	$31.60	$31.60	$31.60
7 purchase totals =	$689.30		$737.8324	$737.84	$737.75	$737.90