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	$148.72	11.384%	$165.6503	$165.65	$165.65	$165.70
Purchase #2	$44.65	4.173%	$46.5132	$46.51	$46.50	$46.50
Purchase #3	$225.31	5.453%	$237.5962	$237.60	$237.60	$237.60
Purchase #4	$167.32	12.583%	$188.3739	$188.37	$188.35	$188.40
Purchase #5	$59.37	7.694%	$63.9379	$63.94	$63.95	$63.90
Purchase #6	$143.54	6.811%	$153.3165	$153.32	$153.30	$153.30
Purchase #7	$217.61	5.709%	$230.0334	$230.03	$230.05	$230.00
7 purchase totals =	$1,006.52		$1,085.4214	$1,085.42	$1,085.40	$1,085.40