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	$88.32	4.647%	$92.4242	$92.42	$92.40	$92.40
Purchase #2	$225.26	13.283%	$255.1813	$255.18	$255.20	$255.20
Purchase #3	$43.67	4.436%	$45.6072	$45.61	$45.60	$45.60
Purchase #4	$164.36	12.323%	$184.6141	$184.61	$184.60	$184.60
Purchase #5	$241.51	3.551%	$250.086	$250.09	$250.10	$250.10
Purchase #6	$118.31	12.251%	$132.8042	$132.80	$132.80	$132.80
Purchase #7	$85.40	6.699%	$91.1209	$91.12	$91.10	$91.10
7 purchase totals =	$966.83		$1,051.8379	$1,051.83	$1,051.80	$1,051.80