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	$162.68	5.823%	$172.1529	$172.15	$172.15	$172.20
Purchase #2	$153.85	5.665%	$162.5656	$162.57	$162.55	$162.60
Purchase #3	$136.69	6.665%	$145.8004	$145.80	$145.80	$145.80
Purchase #4	$79.71	4.441%	$83.2499	$83.25	$83.25	$83.20
Purchase #5	$100.93	10.763%	$111.7931	$111.79	$111.80	$111.80
Purchase #6	$219.99	8.873%	$239.5097	$239.51	$239.50	$239.50
Purchase #7	$196.58	10.341%	$216.9083	$216.91	$216.90	$216.90
7 purchase totals =	$1,050.43		$1,131.9799	$1,131.98	$1,131.95	$1,132.00