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	$141.80	10.680%	$156.9442	$156.94	$156.95	$156.90
Purchase #2	$148.34	10.199%	$163.4692	$163.47	$163.45	$163.50
Purchase #3	$43.26	13.655%	$49.1672	$49.17	$49.15	$49.20
Purchase #4	$89.65	4.309%	$93.513	$93.51	$93.50	$93.50
Purchase #5	$180.29	9.195%	$196.8677	$196.87	$196.85	$196.90
Purchase #6	$92.38	12.396%	$103.8314	$103.83	$103.85	$103.80
Purchase #7	$36.45	6.822%	$38.9366	$38.94	$38.95	$38.90
7 purchase totals =	$732.17		$802.7293	$802.73	$802.70	$802.70