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	$205.56	6.724%	$219.3819	$219.38	$219.40	$219.40
Purchase #2	$18.63	11.338%	$20.7423	$20.74	$20.75	$20.70
Purchase #3	$18.25	7.389%	$19.5985	$19.60	$19.60	$19.60
Purchase #4	$50.60	4.496%	$52.875	$52.88	$52.90	$52.90
Purchase #5	$245.38	12.177%	$275.2599	$275.26	$275.25	$275.30
Purchase #6	$172.68	8.377%	$187.1454	$187.15	$187.15	$187.10
Purchase #7	$247.30	6.593%	$263.6045	$263.60	$263.60	$263.60
7 purchase totals =	$958.40		$1,038.6075	$1,038.61	$1,038.65	$1,038.60