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	$150.74	10.745%	$166.937	$166.94	$166.95	$166.90
Purchase #2	$99.39	12.343%	$111.6577	$111.66	$111.65	$111.70
Purchase #3	$54.39	9.268%	$59.4309	$59.43	$59.45	$59.40
Purchase #4	$75.95	9.233%	$82.9625	$82.96	$82.95	$83.00
Purchase #5	$34.34	7.499%	$36.9152	$36.92	$36.90	$36.90
Purchase #6	$214.98	11.383%	$239.4512	$239.45	$239.45	$239.50
Purchase #7	$50.39	3.833%	$52.3214	$52.32	$52.30	$52.30
7 purchase totals =	$680.18		$749.6759	$749.68	$749.65	$749.70