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	$117.74	8.373%	$127.5984	$127.60	$127.60	$127.60
Purchase #2	$62.38	11.326%	$69.4452	$69.45	$69.45	$69.40
Purchase #3	$87.80	5.324%	$92.4745	$92.47	$92.45	$92.50
Purchase #4	$129.80	11.188%	$144.322	$144.32	$144.30	$144.30
Purchase #5	$74.37	12.254%	$83.4833	$83.48	$83.50	$83.50
Purchase #6	$19.88	10.481%	$21.9636	$21.96	$21.95	$22.00
Purchase #7	$194.64	4.754%	$203.8932	$203.89	$203.90	$203.90
7 purchase totals =	$686.61		$743.1802	$743.17	$743.15	$743.20