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	$126.89	12.262%	$142.4493	$142.45	$142.45	$142.40
Purchase #2	$21.50	11.556%	$23.9845	$23.98	$24.00	$24.00
Purchase #3	$157.46	3.147%	$162.4153	$162.42	$162.40	$162.40
Purchase #4	$6.94	6.822%	$7.4134	$7.41	$7.40	$7.40
Purchase #5	$97.82	6.612%	$104.2879	$104.29	$104.30	$104.30
Purchase #6	$120.26	6.153%	$127.6596	$127.66	$127.65	$127.70
Purchase #7	$92.43	3.425%	$95.5957	$95.60	$95.60	$95.60
7 purchase totals =	$623.30		$663.8057	$663.81	$663.80	$663.80