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	$242.69	4.675%	$254.0358	$254.04	$254.05	$254.00
Purchase #2	$60.54	6.356%	$64.3879	$64.39	$64.40	$64.40
Purchase #3	$158.60	5.175%	$166.8076	$166.81	$166.80	$166.80
Purchase #4	$58.43	7.700%	$62.9291	$62.93	$62.95	$62.90
Purchase #5	$146.57	13.867%	$166.8949	$166.89	$166.90	$166.90
Purchase #6	$122.31	5.312%	$128.8071	$128.81	$128.80	$128.80
Purchase #7	$93.28	11.187%	$103.7152	$103.72	$103.70	$103.70
7 purchase totals =	$882.42		$947.5776	$947.59	$947.60	$947.50