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	$163.28	6.237%	$173.4638	$173.46	$173.45	$173.50
Purchase #2	$82.60	12.312%	$92.7697	$92.77	$92.75	$92.80
Purchase #3	$174.44	10.161%	$192.1648	$192.16	$192.15	$192.20
Purchase #4	$118.29	11.573%	$131.9797	$131.98	$132.00	$132.00
Purchase #5	$95.92	5.814%	$101.4968	$101.50	$101.50	$101.50
Purchase #6	$89.98	9.221%	$98.2771	$98.28	$98.30	$98.30
Purchase #7	$195.61	7.791%	$210.85	$210.85	$210.85	$210.90
7 purchase totals =	$920.12		$1,001.0019	$1,001.00	$1,001.00	$1,001.20