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	$96.29	13.422%	$109.214	$109.21	$109.20	$109.20
Purchase #2	$41.29	13.279%	$46.7729	$46.77	$46.75	$46.80
Purchase #3	$46.86	3.509%	$48.5043	$48.50	$48.50	$48.50
Purchase #4	$232.45	8.188%	$251.483	$251.48	$251.50	$251.50
Purchase #5	$218.49	10.477%	$241.3812	$241.38	$241.40	$241.40
Purchase #6	$146.54	5.321%	$154.3374	$154.34	$154.35	$154.30
Purchase #7	$38.46	4.424%	$40.1615	$40.16	$40.15	$40.20
7 purchase totals =	$820.38		$891.8543	$891.84	$891.85	$891.90