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	$44.38	11.106%	$49.3088	$49.31	$49.30	$49.30
Purchase #2	$40.56	7.409%	$43.5651	$43.57	$43.55	$43.60
Purchase #3	$77.48	6.367%	$82.4132	$82.41	$82.40	$82.40
Purchase #4	$204.99	4.477%	$214.1674	$214.17	$214.15	$214.20
Purchase #5	$134.48	12.463%	$151.2402	$151.24	$151.25	$151.20
Purchase #6	$95.59	6.462%	$101.767	$101.77	$101.75	$101.80
Purchase #7	$66.40	9.309%	$72.5812	$72.58	$72.60	$72.60
7 purchase totals =	$663.88		$715.0429	$715.05	$715.00	$715.10