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	$145.93	7.164%	$156.3844	$156.38	$156.40	$156.40
Purchase #2	$51.34	11.622%	$57.3067	$57.31	$57.30	$57.30
Purchase #3	$170.90	12.551%	$192.3497	$192.35	$192.35	$192.30
Purchase #4	$34.78	6.610%	$37.079	$37.08	$37.10	$37.10
Purchase #5	$158.67	8.438%	$172.0586	$172.06	$172.05	$172.10
Purchase #6	$131.28	9.600%	$143.8829	$143.88	$143.90	$143.90
Purchase #7	$205.36	6.649%	$219.0144	$219.01	$219.00	$219.00
7 purchase totals =	$898.26		$978.0757	$978.07	$978.10	$978.10