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	$152.90	12.769%	$172.4238	$172.42	$172.40	$172.40
Purchase #2	$122.27	3.179%	$126.157	$126.16	$126.15	$126.20
Purchase #3	$156.93	6.153%	$166.5859	$166.59	$166.60	$166.60
Purchase #4	$135.88	11.569%	$151.6	$151.60	$151.60	$151.60
Purchase #5	$248.65	7.360%	$266.9506	$266.95	$266.95	$267.00
Purchase #6	$128.67	13.418%	$145.9349	$145.93	$145.95	$145.90
Purchase #7	$65.59	13.605%	$74.5135	$74.51	$74.50	$74.50
7 purchase totals =	$1,010.89		$1,104.1657	$1,104.16	$1,104.15	$1,104.20