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	$112.58	6.475%	$119.8696	$119.87	$119.85	$119.90
Purchase #2	$24.60	11.141%	$27.3407	$27.34	$27.35	$27.30
Purchase #3	$129.38	10.311%	$142.7204	$142.72	$142.70	$142.70
Purchase #4	$98.29	13.588%	$111.6456	$111.65	$111.65	$111.60
Purchase #5	$46.32	12.625%	$52.1679	$52.17	$52.15	$52.20
Purchase #6	$138.25	3.131%	$142.5786	$142.58	$142.60	$142.60
Purchase #7	$33.36	7.198%	$35.7613	$35.76	$35.75	$35.80
7 purchase totals =	$582.78		$632.0841	$632.09	$632.05	$632.10