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	$214.82	13.698%	$244.246	$244.25	$244.25	$244.20
Purchase #2	$29.38	7.807%	$31.6737	$31.67	$31.65	$31.70
Purchase #3	$40.66	5.863%	$43.0439	$43.04	$43.05	$43.00
Purchase #4	$53.67	11.462%	$59.8217	$59.82	$59.80	$59.80
Purchase #5	$22.64	3.450%	$23.4211	$23.42	$23.40	$23.40
Purchase #6	$79.56	3.382%	$82.2507	$82.25	$82.25	$82.30
Purchase #7	$152.84	3.576%	$158.3056	$158.31	$158.30	$158.30
7 purchase totals =	$593.57		$642.7627	$642.76	$642.70	$642.70