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	$228.65	10.705%	$253.127	$253.13	$253.15	$253.10
Purchase #2	$96.86	7.423%	$104.0499	$104.05	$104.05	$104.00
Purchase #3	$38.65	5.806%	$40.894	$40.89	$40.90	$40.90
Purchase #4	$100.30	6.835%	$107.1555	$107.16	$107.15	$107.20
Purchase #5	$155.83	13.107%	$176.2546	$176.25	$176.25	$176.30
Purchase #6	$114.66	11.459%	$127.7989	$127.80	$127.80	$127.80
Purchase #7	$10.68	5.721%	$11.291	$11.29	$11.30	$11.30
7 purchase totals =	$745.63		$820.5709	$820.57	$820.60	$820.60