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	$151.86	10.438%	$167.7111	$167.71	$167.70	$167.70
Purchase #2	$160.90	7.832%	$173.5017	$173.50	$173.50	$173.50
Purchase #3	$103.28	8.380%	$111.9349	$111.93	$111.95	$111.90
Purchase #4	$131.94	13.687%	$149.9986	$150.00	$150.00	$150.00
Purchase #5	$60.85	12.305%	$68.3376	$68.34	$68.35	$68.30
Purchase #6	$242.96	8.428%	$263.4367	$263.44	$263.45	$263.40
Purchase #7	$230.27	11.541%	$256.8455	$256.85	$256.85	$256.80
7 purchase totals =	$1,082.06		$1,191.7661	$1,191.77	$1,191.80	$1,191.60