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	$227.39	6.241%	$241.5814	$241.58	$241.60	$241.60
Purchase #2	$37.98	9.703%	$41.6652	$41.67	$41.65	$41.70
Purchase #3	$11.55	7.185%	$12.3799	$12.38	$12.40	$12.40
Purchase #4	$29.91	9.816%	$32.846	$32.85	$32.85	$32.80
Purchase #5	$151.42	9.448%	$165.7262	$165.73	$165.75	$165.70
Purchase #6	$36.42	6.679%	$38.8525	$38.85	$38.85	$38.90
Purchase #7	$233.76	5.810%	$247.3415	$247.34	$247.35	$247.30
7 purchase totals =	$728.43		$780.3927	$780.40	$780.45	$780.40