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	$206.85	10.624%	$228.8257	$228.83	$228.85	$228.80
Purchase #2	$185.61	10.718%	$205.5037	$205.50	$205.50	$205.50
Purchase #3	$126.86	6.303%	$134.856	$134.86	$134.85	$134.90
Purchase #4	$171.56	9.439%	$187.7535	$187.75	$187.75	$187.80
Purchase #5	$45.39	9.703%	$49.7942	$49.79	$49.80	$49.80
Purchase #6	$20.49	4.665%	$21.4459	$21.45	$21.45	$21.40
Purchase #7	$165.46	8.320%	$179.2263	$179.23	$179.25	$179.20
7 purchase totals =	$922.22		$1,007.4053	$1,007.41	$1,007.45	$1,007.40