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	$154.55	4.189%	$161.0241	$161.02	$161.00	$161.00
Purchase #2	$59.94	13.150%	$67.8221	$67.82	$67.80	$67.80
Purchase #3	$116.26	13.360%	$131.7923	$131.79	$131.80	$131.80
Purchase #4	$74.92	8.509%	$81.2949	$81.29	$81.30	$81.30
Purchase #5	$179.32	5.610%	$189.3799	$189.38	$189.40	$189.40
Purchase #6	$243.74	11.191%	$271.0169	$271.02	$271.00	$271.00
Purchase #7	$178.88	3.684%	$185.4699	$185.47	$185.45	$185.50
7 purchase totals =	$1,007.61		$1,087.8001	$1,087.79	$1,087.75	$1,087.80