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	$212.25	9.162%	$231.6963	$231.70	$231.70	$231.70
Purchase #2	$128.41	6.513%	$136.7733	$136.77	$136.75	$136.80
Purchase #3	$221.69	10.627%	$245.249	$245.25	$245.25	$245.20
Purchase #4	$54.50	5.478%	$57.4855	$57.49	$57.50	$57.50
Purchase #5	$51.82	3.540%	$53.6544	$53.65	$53.65	$53.70
Purchase #6	$208.69	10.603%	$230.8174	$230.82	$230.80	$230.80
Purchase #7	$128.76	12.209%	$144.4803	$144.48	$144.50	$144.50
7 purchase totals =	$1,006.12		$1,100.1562	$1,100.16	$1,100.15	$1,100.20