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	$110.42	10.136%	$121.6122	$121.61	$121.60	$121.60
Purchase #2	$7.35	11.212%	$8.1741	$8.17	$8.15	$8.20
Purchase #3	$70.97	8.296%	$76.8577	$76.86	$76.85	$76.90
Purchase #4	$77.90	6.478%	$82.9464	$82.95	$82.95	$82.90
Purchase #5	$18.69	11.642%	$20.8659	$20.87	$20.85	$20.90
Purchase #6	$103.79	7.581%	$111.6583	$111.66	$111.65	$111.70
Purchase #7	$218.87	4.800%	$229.3758	$229.38	$229.40	$229.40
7 purchase totals =	$607.99		$651.4904	$651.50	$651.45	$651.60