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	$151.43	13.553%	$171.9533	$171.95	$171.95	$172.00
Purchase #2	$33.42	13.377%	$37.8906	$37.89	$37.90	$37.90
Purchase #3	$49.49	5.756%	$52.3386	$52.34	$52.35	$52.30
Purchase #4	$177.65	6.154%	$188.5826	$188.58	$188.60	$188.60
Purchase #5	$242.28	4.209%	$252.4776	$252.48	$252.50	$252.50
Purchase #6	$46.66	11.291%	$51.9284	$51.93	$51.95	$51.90
Purchase #7	$87.38	13.147%	$98.8678	$98.87	$98.85	$98.90
7 purchase totals =	$788.31		$854.0389	$854.04	$854.10	$854.10