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	$105.29	10.408%	$116.2486	$116.25	$116.25	$116.20
Purchase #2	$92.35	11.510%	$102.9795	$102.98	$103.00	$103.00
Purchase #3	$133.49	5.261%	$140.5129	$140.51	$140.50	$140.50
Purchase #4	$128.73	3.610%	$133.3772	$133.38	$133.40	$133.40
Purchase #5	$166.55	4.127%	$173.4235	$173.42	$173.40	$173.40
Purchase #6	$127.62	12.739%	$143.8775	$143.88	$143.90	$143.90
Purchase #7	$121.28	4.616%	$126.8783	$126.88	$126.90	$126.90
7 purchase totals =	$875.31		$937.2975	$937.30	$937.35	$937.30