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	$207.95	10.456%	$229.6933	$229.69	$229.70	$229.70
Purchase #2	$28.92	8.303%	$31.3212	$31.32	$31.30	$31.30
Purchase #3	$65.86	3.498%	$68.1638	$68.16	$68.15	$68.20
Purchase #4	$48.71	8.309%	$52.7573	$52.76	$52.75	$52.80
Purchase #5	$224.88	7.695%	$242.1845	$242.18	$242.20	$242.20
Purchase #6	$128.41	11.765%	$143.5174	$143.52	$143.50	$143.50
Purchase #7	$185.83	13.317%	$210.577	$210.58	$210.60	$210.60
7 purchase totals =	$890.56		$978.2145	$978.21	$978.20	$978.30