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	$95.69	8.339%	$103.6696	$103.67	$103.65	$103.70
Purchase #2	$177.64	10.867%	$196.9441	$196.94	$196.95	$196.90
Purchase #3	$40.88	5.371%	$43.0757	$43.08	$43.10	$43.10
Purchase #4	$50.42	5.204%	$53.0439	$53.04	$53.05	$53.00
Purchase #5	$153.52	12.787%	$173.1506	$173.15	$173.15	$173.20
Purchase #6	$36.78	8.488%	$39.9019	$39.90	$39.90	$39.90
Purchase #7	$250.48	3.784%	$259.9582	$259.96	$259.95	$260.00
7 purchase totals =	$805.41		$869.7440	$869.74	$869.75	$869.80