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	$116.69	13.466%	$132.4035	$132.40	$132.40	$132.40
Purchase #2	$164.92	4.551%	$172.4255	$172.43	$172.45	$172.40
Purchase #3	$162.29	7.466%	$174.4066	$174.41	$174.40	$174.40
Purchase #4	$189.43	10.529%	$209.3751	$209.38	$209.40	$209.40
Purchase #5	$122.30	4.771%	$128.1349	$128.13	$128.15	$128.10
Purchase #6	$144.88	8.706%	$157.4933	$157.49	$157.50	$157.50
Purchase #7	$41.66	9.403%	$45.5773	$45.58	$45.60	$45.60
7 purchase totals =	$942.17		$1,019.8162	$1,019.82	$1,019.90	$1,019.80