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	$49.45	10.795%	$54.7881	$54.79	$54.80	$54.80
Purchase #2	$10.45	4.826%	$10.9543	$10.95	$10.95	$11.00
Purchase #3	$150.83	11.717%	$168.5028	$168.50	$168.50	$168.50
Purchase #4	$230.34	4.790%	$241.3733	$241.37	$241.35	$241.40
Purchase #5	$67.33	13.607%	$76.4916	$76.49	$76.50	$76.50
Purchase #6	$219.36	10.379%	$242.1274	$242.13	$242.15	$242.10
Purchase #7	$197.87	3.768%	$205.3257	$205.33	$205.35	$205.30
7 purchase totals =	$925.63		$999.5632	$999.56	$999.60	$999.60