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	$183.97	4.624%	$192.4768	$192.48	$192.50	$192.50
Purchase #2	$91.63	9.767%	$100.5795	$100.58	$100.60	$100.60
Purchase #3	$107.54	3.462%	$111.263	$111.26	$111.25	$111.30
Purchase #4	$148.80	8.807%	$161.9048	$161.90	$161.90	$161.90
Purchase #5	$245.97	10.191%	$271.0368	$271.04	$271.05	$271.00
Purchase #6	$119.58	6.499%	$127.3515	$127.35	$127.35	$127.40
Purchase #7	$107.77	11.200%	$119.8402	$119.84	$119.85	$119.80
7 purchase totals =	$1,005.26		$1,084.4526	$1,084.45	$1,084.50	$1,084.50