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	$221.49	9.816%	$243.2315	$243.23	$243.25	$243.20
Purchase #2	$81.73	11.204%	$90.887	$90.89	$90.90	$90.90
Purchase #3	$223.80	12.846%	$252.5493	$252.55	$252.55	$252.50
Purchase #4	$37.52	4.407%	$39.1735	$39.17	$39.15	$39.20
Purchase #5	$70.62	8.493%	$76.6178	$76.62	$76.60	$76.60
Purchase #6	$173.94	12.734%	$196.0895	$196.09	$196.10	$196.10
Purchase #7	$98.97	4.541%	$103.4642	$103.46	$103.45	$103.50
7 purchase totals =	$908.07		$1,002.0128	$1,002.01	$1,002.00	$1,002.00