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	$72.80	8.817%	$79.2188	$79.22	$79.20	$79.20
Purchase #2	$66.68	13.229%	$75.5011	$75.50	$75.50	$75.50
Purchase #3	$142.91	7.215%	$153.221	$153.22	$153.20	$153.20
Purchase #4	$90.68	13.683%	$103.0877	$103.09	$103.10	$103.10
Purchase #5	$79.41	12.737%	$89.5245	$89.52	$89.50	$89.50
Purchase #6	$43.47	4.502%	$45.427	$45.43	$45.45	$45.40
Purchase #7	$157.45	13.819%	$179.208	$179.21	$179.20	$179.20
7 purchase totals =	$653.40		$725.1881	$725.19	$725.15	$725.10