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	$32.35	5.610%	$34.1648	$34.16	$34.15	$34.20
Purchase #2	$80.44	7.618%	$86.5679	$86.57	$86.55	$86.60
Purchase #3	$115.55	10.307%	$127.4597	$127.46	$127.45	$127.50
Purchase #4	$100.92	10.579%	$111.5963	$111.60	$111.60	$111.60
Purchase #5	$57.37	10.295%	$63.2762	$63.28	$63.30	$63.30
Purchase #6	$14.64	13.610%	$16.6325	$16.63	$16.65	$16.60
Purchase #7	$186.74	10.770%	$206.8519	$206.85	$206.85	$206.90
7 purchase totals =	$588.01		$646.5493	$646.55	$646.55	$646.70