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	$179.74	9.370%	$196.5816	$196.58	$196.60	$196.60
Purchase #2	$109.83	10.454%	$121.3116	$121.31	$121.30	$121.30
Purchase #3	$247.82	5.811%	$262.2208	$262.22	$262.20	$262.20
Purchase #4	$136.80	13.671%	$155.5019	$155.50	$155.50	$155.50
Purchase #5	$162.30	6.344%	$172.5963	$172.60	$172.60	$172.60
Purchase #6	$147.78	11.714%	$165.0909	$165.09	$165.10	$165.10
Purchase #7	$77.74	12.292%	$87.2958	$87.30	$87.30	$87.30
7 purchase totals =	$1,062.01		$1,160.5989	$1,160.60	$1,160.60	$1,160.60