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	$33.31	8.309%	$36.0777	$36.08	$36.10	$36.10
Purchase #2	$61.49	6.760%	$65.6467	$65.65	$65.65	$65.60
Purchase #3	$10.42	10.571%	$11.5215	$11.52	$11.50	$11.50
Purchase #4	$90.33	11.770%	$100.9618	$100.96	$100.95	$101.00
Purchase #5	$238.70	9.172%	$260.5936	$260.59	$260.60	$260.60
Purchase #6	$134.47	10.717%	$148.8811	$148.88	$148.90	$148.90
Purchase #7	$119.76	3.342%	$123.7624	$123.76	$123.75	$123.80
7 purchase totals =	$688.48		$747.4448	$747.44	$747.45	$747.50