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	$161.49	12.680%	$181.9669	$181.97	$181.95	$182.00
Purchase #2	$163.28	5.231%	$171.8212	$171.82	$171.80	$171.80
Purchase #3	$40.79	11.467%	$45.4674	$45.47	$45.45	$45.50
Purchase #4	$112.61	10.763%	$124.7302	$124.73	$124.75	$124.70
Purchase #5	$119.91	3.266%	$123.8263	$123.83	$123.85	$123.80
Purchase #6	$212.90	13.514%	$241.6713	$241.67	$241.65	$241.70
Purchase #7	$80.25	11.294%	$89.3134	$89.31	$89.30	$89.30
7 purchase totals =	$891.23		$978.7967	$978.80	$978.75	$978.80