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	$97.94	10.774%	$108.4921	$108.49	$108.50	$108.50
Purchase #2	$116.64	9.269%	$127.4514	$127.45	$127.45	$127.50
Purchase #3	$206.94	5.848%	$219.0419	$219.04	$219.05	$219.00
Purchase #4	$120.67	6.343%	$128.3241	$128.32	$128.30	$128.30
Purchase #5	$23.39	9.640%	$25.6448	$25.64	$25.65	$25.60
Purchase #6	$160.83	8.639%	$174.7241	$174.72	$174.70	$174.70
Purchase #7	$121.34	5.364%	$127.8487	$127.85	$127.85	$127.80
7 purchase totals =	$847.75		$911.5271	$911.51	$911.50	$911.40