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	$92.38	8.140%	$99.8997	$99.90	$99.90	$99.90
Purchase #2	$92.51	6.315%	$98.352	$98.35	$98.35	$98.40
Purchase #3	$97.80	5.653%	$103.3286	$103.33	$103.35	$103.30
Purchase #4	$192.77	11.444%	$214.8306	$214.83	$214.85	$214.80
Purchase #5	$68.95	4.426%	$72.0017	$72.00	$72.00	$72.00
Purchase #6	$138.83	9.719%	$152.3229	$152.32	$152.30	$152.30
Purchase #7	$146.44	5.471%	$154.4517	$154.45	$154.45	$154.50
7 purchase totals =	$829.68		$895.1872	$895.18	$895.20	$895.20