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	$63.78	11.556%	$71.1504	$71.15	$71.15	$71.20
Purchase #2	$164.38	12.179%	$184.3998	$184.40	$184.40	$184.40
Purchase #3	$158.52	10.647%	$175.3976	$175.40	$175.40	$175.40
Purchase #4	$58.55	3.268%	$60.4634	$60.46	$60.45	$60.50
Purchase #5	$50.92	12.758%	$57.4164	$57.42	$57.40	$57.40
Purchase #6	$169.74	4.117%	$176.7282	$176.73	$176.75	$176.70
Purchase #7	$37.49	6.769%	$40.0277	$40.03	$40.05	$40.00
7 purchase totals =	$703.38		$765.5835	$765.59	$765.60	$765.60