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	$152.38	7.504%	$163.8146	$163.81	$163.80	$163.80
Purchase #2	$19.34	4.365%	$20.1842	$20.18	$20.20	$20.20
Purchase #3	$143.46	4.849%	$150.4164	$150.42	$150.40	$150.40
Purchase #4	$208.66	5.347%	$219.8171	$219.82	$219.80	$219.80
Purchase #5	$89.61	12.169%	$100.5146	$100.51	$100.50	$100.50
Purchase #6	$191.65	7.205%	$205.4584	$205.46	$205.45	$205.50
Purchase #7	$100.35	8.644%	$109.0243	$109.02	$109.00	$109.00
7 purchase totals =	$905.45		$969.2296	$969.22	$969.15	$969.20