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	$128.60	10.536%	$142.1493	$142.15	$142.15	$142.10
Purchase #2	$195.88	9.322%	$214.1399	$214.14	$214.15	$214.10
Purchase #3	$229.64	11.804%	$256.7467	$256.75	$256.75	$256.70
Purchase #4	$152.56	13.465%	$173.1022	$173.10	$173.10	$173.10
Purchase #5	$34.77	8.404%	$37.6921	$37.69	$37.70	$37.70
Purchase #6	$52.48	5.146%	$55.1806	$55.18	$55.20	$55.20
Purchase #7	$196.93	4.159%	$205.1203	$205.12	$205.10	$205.10
7 purchase totals =	$990.86		$1,084.1311	$1,084.13	$1,084.15	$1,084.00