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	$34.65	8.648%	$37.6465	$37.65	$37.65	$37.60
Purchase #2	$228.28	8.218%	$247.0401	$247.04	$247.05	$247.00
Purchase #3	$247.83	3.155%	$255.649	$255.65	$255.65	$255.60
Purchase #4	$128.81	12.156%	$144.4681	$144.47	$144.45	$144.50
Purchase #5	$175.47	7.592%	$188.7917	$188.79	$188.80	$188.80
Purchase #6	$200.40	9.163%	$218.7627	$218.76	$218.75	$218.80
Purchase #7	$120.93	9.280%	$132.1523	$132.15	$132.15	$132.20
7 purchase totals =	$1,136.37		$1,224.5104	$1,224.51	$1,224.50	$1,224.50