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	$50.53	5.644%	$53.3819	$53.38	$53.40	$53.40
Purchase #2	$175.40	6.626%	$187.022	$187.02	$187.00	$187.00
Purchase #3	$211.91	8.505%	$229.9329	$229.93	$229.95	$229.90
Purchase #4	$229.25	11.335%	$255.2355	$255.24	$255.25	$255.20
Purchase #5	$119.38	4.584%	$124.8524	$124.85	$124.85	$124.90
Purchase #6	$66.42	8.322%	$71.9475	$71.95	$71.95	$71.90
Purchase #7	$111.85	10.170%	$123.2251	$123.23	$123.25	$123.20
7 purchase totals =	$964.74		$1,045.5973	$1,045.60	$1,045.65	$1,045.50