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	$10.87	9.739%	$11.9286	$11.93	$11.95	$11.90
Purchase #2	$98.78	7.129%	$105.822	$105.82	$105.80	$105.80
Purchase #3	$35.73	3.795%	$37.086	$37.09	$37.10	$37.10
Purchase #4	$136.67	6.274%	$145.2447	$145.24	$145.25	$145.20
Purchase #5	$120.75	11.338%	$134.4406	$134.44	$134.45	$134.40
Purchase #6	$155.59	3.858%	$161.5927	$161.59	$161.60	$161.60
Purchase #7	$105.84	3.119%	$109.1411	$109.14	$109.15	$109.10
7 purchase totals =	$664.23		$705.2557	$705.25	$705.30	$705.10