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	$228.50	9.212%	$249.5494	$249.55	$249.55	$249.50
Purchase #2	$34.42	7.668%	$37.0593	$37.06	$37.05	$37.10
Purchase #3	$97.33	5.573%	$102.7542	$102.75	$102.75	$102.80
Purchase #4	$12.79	13.172%	$14.4747	$14.47	$14.45	$14.50
Purchase #5	$57.79	8.825%	$62.89	$62.89	$62.90	$62.90
Purchase #6	$132.27	3.641%	$137.086	$137.09	$137.10	$137.10
Purchase #7	$230.43	5.448%	$242.9838	$242.98	$243.00	$243.00
7 purchase totals =	$793.53		$846.7974	$846.79	$846.80	$846.90