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	$150.35	5.395%	$158.4614	$158.46	$158.45	$158.50
Purchase #2	$145.50	5.747%	$153.8619	$153.86	$153.85	$153.90
Purchase #3	$175.82	6.615%	$187.4505	$187.45	$187.45	$187.50
Purchase #4	$127.60	5.224%	$134.2658	$134.27	$134.25	$134.30
Purchase #5	$207.34	12.653%	$233.5747	$233.57	$233.55	$233.60
Purchase #6	$56.77	13.324%	$64.334	$64.33	$64.35	$64.30
Purchase #7	$208.64	11.573%	$232.7859	$232.79	$232.80	$232.80
7 purchase totals =	$1,072.02		$1,164.7342	$1,164.73	$1,164.70	$1,164.90