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	$225.78	3.721%	$234.1813	$234.18	$234.20	$234.20
Purchase #2	$238.39	8.396%	$258.4052	$258.41	$258.40	$258.40
Purchase #3	$111.41	13.163%	$126.0749	$126.07	$126.05	$126.10
Purchase #4	$183.93	11.542%	$205.1592	$205.16	$205.15	$205.20
Purchase #5	$35.69	13.693%	$40.577	$40.58	$40.60	$40.60
Purchase #6	$130.39	10.516%	$144.1018	$144.10	$144.10	$144.10
Purchase #7	$59.78	10.125%	$65.8327	$65.83	$65.85	$65.80
7 purchase totals =	$985.37		$1,074.3321	$1,074.33	$1,074.35	$1,074.40