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	$158.68	6.471%	$168.9482	$168.95	$168.95	$168.90
Purchase #2	$37.80	12.646%	$42.5802	$42.58	$42.60	$42.60
Purchase #3	$75.26	13.105%	$85.1228	$85.12	$85.10	$85.10
Purchase #4	$78.50	12.289%	$88.1469	$88.15	$88.15	$88.10
Purchase #5	$43.38	10.165%	$47.7896	$47.79	$47.80	$47.80
Purchase #6	$229.31	10.213%	$252.7294	$252.73	$252.75	$252.70
Purchase #7	$108.83	5.122%	$114.4043	$114.40	$114.40	$114.40
7 purchase totals =	$731.76		$799.7214	$799.72	$799.75	$799.60