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	$112.83	6.209%	$119.8356	$119.84	$119.85	$119.80
Purchase #2	$53.41	10.126%	$58.8183	$58.82	$58.80	$58.80
Purchase #3	$129.65	3.685%	$134.4276	$134.43	$134.45	$134.40
Purchase #4	$188.30	12.411%	$211.6699	$211.67	$211.65	$211.70
Purchase #5	$132.31	6.666%	$141.1298	$141.13	$141.15	$141.10
Purchase #6	$32.92	4.246%	$34.3178	$34.32	$34.30	$34.30
Purchase #7	$100.47	10.771%	$111.2916	$111.29	$111.30	$111.30
7 purchase totals =	$749.89		$811.4906	$811.50	$811.50	$811.40