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	$160.41	4.810%	$168.1257	$168.13	$168.15	$168.10
Purchase #2	$131.87	6.603%	$140.5774	$140.58	$140.60	$140.60
Purchase #3	$116.70	11.835%	$130.5114	$130.51	$130.50	$130.50
Purchase #4	$159.52	12.554%	$179.5461	$179.55	$179.55	$179.50
Purchase #5	$22.63	6.751%	$24.1578	$24.16	$24.15	$24.20
Purchase #6	$48.89	7.227%	$52.4233	$52.42	$52.40	$52.40
Purchase #7	$91.60	10.189%	$100.9331	$100.93	$100.95	$100.90
7 purchase totals =	$731.62		$796.2748	$796.28	$796.30	$796.20