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	$73.55	10.670%	$81.3978	$81.40	$81.40	$81.40
Purchase #2	$78.38	6.677%	$83.6134	$83.61	$83.60	$83.60
Purchase #3	$112.45	7.470%	$120.85	$120.85	$120.85	$120.90
Purchase #4	$98.30	13.323%	$111.3965	$111.40	$111.40	$111.40
Purchase #5	$224.25	5.854%	$237.3776	$237.38	$237.40	$237.40
Purchase #6	$45.77	6.251%	$48.6311	$48.63	$48.65	$48.60
Purchase #7	$32.88	4.444%	$34.3412	$34.34	$34.35	$34.30
7 purchase totals =	$665.58		$717.6076	$717.61	$717.65	$717.60