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	$174.94	12.254%	$196.3771	$196.38	$196.40	$196.40
Purchase #2	$137.58	12.273%	$154.4652	$154.47	$154.45	$154.50
Purchase #3	$230.89	3.455%	$238.8672	$238.87	$238.85	$238.90
Purchase #4	$243.80	9.692%	$267.4291	$267.43	$267.45	$267.40
Purchase #5	$85.50	6.162%	$90.7685	$90.77	$90.75	$90.80
Purchase #6	$137.46	12.129%	$154.1325	$154.13	$154.15	$154.10
Purchase #7	$163.25	7.551%	$175.577	$175.58	$175.60	$175.60
7 purchase totals =	$1,173.42		$1,277.6166	$1,277.63	$1,277.65	$1,277.70