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	$119.35	6.677%	$127.319	$127.32	$127.30	$127.30
Purchase #2	$86.35	5.555%	$91.1467	$91.15	$91.15	$91.10
Purchase #3	$17.42	3.741%	$18.0717	$18.07	$18.05	$18.10
Purchase #4	$200.31	8.463%	$217.2622	$217.26	$217.25	$217.30
Purchase #5	$80.44	6.641%	$85.782	$85.78	$85.80	$85.80
Purchase #6	$58.72	13.807%	$66.8275	$66.83	$66.85	$66.80
Purchase #7	$248.32	4.154%	$258.6352	$258.64	$258.65	$258.60
7 purchase totals =	$810.91		$865.0443	$865.05	$865.05	$865.00