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	$101.89	9.268%	$111.3332	$111.33	$111.35	$111.30
Purchase #2	$127.32	13.869%	$144.978	$144.98	$145.00	$145.00
Purchase #3	$28.33	13.323%	$32.1044	$32.10	$32.10	$32.10
Purchase #4	$131.70	4.121%	$137.1274	$137.13	$137.15	$137.10
Purchase #5	$204.82	5.209%	$215.4891	$215.49	$215.50	$215.50
Purchase #6	$221.83	3.552%	$229.7094	$229.71	$229.70	$229.70
Purchase #7	$146.57	11.203%	$162.9902	$162.99	$163.00	$163.00
7 purchase totals =	$962.46		$1,033.7317	$1,033.73	$1,033.80	$1,033.70