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	$137.93	11.239%	$153.432	$153.43	$153.45	$153.40
Purchase #2	$207.62	12.346%	$233.2528	$233.25	$233.25	$233.30
Purchase #3	$123.49	12.334%	$138.7213	$138.72	$138.70	$138.70
Purchase #4	$30.29	7.208%	$32.4733	$32.47	$32.45	$32.50
Purchase #5	$211.87	9.239%	$231.4447	$231.44	$231.45	$231.40
Purchase #6	$213.62	4.310%	$222.827	$222.83	$222.85	$222.80
Purchase #7	$121.99	4.497%	$127.4759	$127.48	$127.50	$127.50
7 purchase totals =	$1,046.81		$1,139.6270	$1,139.62	$1,139.65	$1,139.60