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	$160.43	8.144%	$173.4954	$173.50	$173.50	$173.50
Purchase #2	$79.88	10.340%	$88.1396	$88.14	$88.15	$88.10
Purchase #3	$224.90	7.554%	$241.8889	$241.89	$241.90	$241.90
Purchase #4	$238.90	6.459%	$254.3306	$254.33	$254.35	$254.30
Purchase #5	$95.33	10.338%	$105.1852	$105.19	$105.20	$105.20
Purchase #6	$133.83	12.203%	$150.1613	$150.16	$150.15	$150.20
Purchase #7	$218.56	13.103%	$247.1979	$247.20	$247.20	$247.20
7 purchase totals =	$1,151.83		$1,260.3989	$1,260.41	$1,260.45	$1,260.40