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	$111.87	4.203%	$116.5719	$116.57	$116.55	$116.60
Purchase #2	$53.98	10.503%	$59.6495	$59.65	$59.65	$59.60
Purchase #3	$162.68	3.108%	$167.7361	$167.74	$167.75	$167.70
Purchase #4	$81.58	9.813%	$89.5854	$89.59	$89.60	$89.60
Purchase #5	$214.61	13.597%	$243.7905	$243.79	$243.80	$243.80
Purchase #6	$145.97	10.622%	$161.4749	$161.47	$161.45	$161.50
Purchase #7	$187.83	5.685%	$198.5081	$198.51	$198.50	$198.50
7 purchase totals =	$958.52		$1,037.3164	$1,037.32	$1,037.30	$1,037.30