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	$244.68	9.153%	$267.0756	$267.08	$267.10	$267.10
Purchase #2	$48.73	3.538%	$50.4541	$50.45	$50.45	$50.50
Purchase #3	$80.26	13.133%	$90.8005	$90.80	$90.80	$90.80
Purchase #4	$27.52	6.631%	$29.3449	$29.34	$29.35	$29.30
Purchase #5	$166.78	10.792%	$184.7789	$184.78	$184.80	$184.80
Purchase #6	$191.83	7.138%	$205.5228	$205.52	$205.50	$205.50
Purchase #7	$167.50	5.370%	$176.4948	$176.49	$176.50	$176.50
7 purchase totals =	$927.30		$1,004.4716	$1,004.46	$1,004.50	$1,004.50