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	$105.88	5.322%	$111.5149	$111.51	$111.50	$111.50
Purchase #2	$14.54	3.714%	$15.08	$15.08	$15.10	$15.10
Purchase #3	$54.83	3.563%	$56.7836	$56.78	$56.80	$56.80
Purchase #4	$168.29	11.576%	$187.7713	$187.77	$187.75	$187.80
Purchase #5	$237.65	4.858%	$249.195	$249.20	$249.20	$249.20
Purchase #6	$250.95	12.527%	$282.3865	$282.39	$282.40	$282.40
Purchase #7	$242.37	8.551%	$263.0951	$263.10	$263.10	$263.10
7 purchase totals =	$1,074.51		$1,165.8264	$1,165.83	$1,165.85	$1,165.90