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	$120.65	11.693%	$134.7576	$134.76	$134.75	$134.80
Purchase #2	$100.92	10.169%	$111.1826	$111.18	$111.20	$111.20
Purchase #3	$32.62	5.291%	$34.3459	$34.35	$34.35	$34.30
Purchase #4	$67.90	6.274%	$72.16	$72.16	$72.15	$72.20
Purchase #5	$181.50	13.187%	$205.4344	$205.43	$205.45	$205.40
Purchase #6	$63.65	10.138%	$70.1028	$70.10	$70.10	$70.10
Purchase #7	$144.35	7.759%	$155.5501	$155.55	$155.55	$155.60
7 purchase totals =	$711.59		$783.5334	$783.53	$783.55	$783.60