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	$204.62	10.632%	$226.3752	$226.38	$226.40	$226.40
Purchase #2	$88.47	6.766%	$94.4559	$94.46	$94.45	$94.50
Purchase #3	$121.61	4.517%	$127.1031	$127.10	$127.10	$127.10
Purchase #4	$242.51	6.582%	$258.472	$258.47	$258.45	$258.50
Purchase #5	$191.27	7.334%	$205.2977	$205.30	$205.30	$205.30
Purchase #6	$168.64	9.619%	$184.8615	$184.86	$184.85	$184.90
Purchase #7	$178.44	12.615%	$200.9502	$200.95	$200.95	$201.00
7 purchase totals =	$1,195.56		$1,297.5156	$1,297.52	$1,297.50	$1,297.70