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	$217.56	5.829%	$230.2416	$230.24	$230.25	$230.20
Purchase #2	$79.50	3.544%	$82.3175	$82.32	$82.30	$82.30
Purchase #3	$94.97	6.194%	$100.8524	$100.85	$100.85	$100.90
Purchase #4	$74.49	4.859%	$78.1095	$78.11	$78.10	$78.10
Purchase #5	$9.94	9.373%	$10.8717	$10.87	$10.85	$10.90
Purchase #6	$95.76	8.488%	$103.8881	$103.89	$103.90	$103.90
Purchase #7	$64.28	10.127%	$70.7896	$70.79	$70.80	$70.80
7 purchase totals =	$636.50		$677.0704	$677.07	$677.05	$677.10