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	$14.32	8.709%	$15.5671	$15.57	$15.55	$15.60
Purchase #2	$237.50	11.577%	$264.9954	$265.00	$265.00	$265.00
Purchase #3	$115.51	10.619%	$127.776	$127.78	$127.80	$127.80
Purchase #4	$59.53	11.699%	$66.4944	$66.49	$66.50	$66.50
Purchase #5	$19.78	7.599%	$21.2831	$21.28	$21.30	$21.30
Purchase #6	$154.48	4.169%	$160.9203	$160.92	$160.90	$160.90
Purchase #7	$163.74	7.678%	$176.312	$176.31	$176.30	$176.30
7 purchase totals =	$764.86		$833.3483	$833.35	$833.35	$833.40