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	$189.88	3.611%	$196.7366	$196.74	$196.75	$196.70
Purchase #2	$31.25	3.262%	$32.2694	$32.27	$32.25	$32.30
Purchase #3	$46.70	6.738%	$49.8466	$49.85	$49.85	$49.80
Purchase #4	$41.52	10.696%	$45.961	$45.96	$45.95	$46.00
Purchase #5	$21.91	12.324%	$24.6102	$24.61	$24.60	$24.60
Purchase #6	$186.87	3.854%	$194.072	$194.07	$194.05	$194.10
Purchase #7	$38.92	8.602%	$42.2679	$42.27	$42.25	$42.30
7 purchase totals =	$557.05		$585.7637	$585.77	$585.70	$585.80