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	$147.29	7.796%	$158.7727	$158.77	$158.75	$158.80
Purchase #2	$92.25	6.429%	$98.1808	$98.18	$98.20	$98.20
Purchase #3	$138.95	10.809%	$153.9691	$153.97	$153.95	$154.00
Purchase #4	$106.35	4.463%	$111.0964	$111.10	$111.10	$111.10
Purchase #5	$78.67	4.812%	$82.4556	$82.46	$82.45	$82.50
Purchase #6	$58.77	12.498%	$66.1151	$66.12	$66.10	$66.10
Purchase #7	$98.73	5.621%	$104.2796	$104.28	$104.30	$104.30
7 purchase totals =	$721.01		$774.8693	$774.88	$774.85	$775.00