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	$114.83	7.537%	$123.4847	$123.48	$123.50	$123.50
Purchase #2	$32.50	5.485%	$34.2826	$34.28	$34.30	$34.30
Purchase #3	$27.86	7.341%	$29.9052	$29.91	$29.90	$29.90
Purchase #4	$127.56	7.555%	$137.1972	$137.20	$137.20	$137.20
Purchase #5	$230.38	11.194%	$256.1687	$256.17	$256.15	$256.20
Purchase #6	$62.94	9.219%	$68.7424	$68.74	$68.75	$68.70
Purchase #7	$112.66	3.442%	$116.5378	$116.54	$116.55	$116.50
7 purchase totals =	$708.73		$766.3186	$766.32	$766.35	$766.30