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	$95.92	9.786%	$105.3067	$105.31	$105.30	$105.30
Purchase #2	$180.52	5.309%	$190.1038	$190.10	$190.10	$190.10
Purchase #3	$54.47	10.399%	$60.1343	$60.13	$60.15	$60.10
Purchase #4	$208.54	5.129%	$219.236	$219.24	$219.25	$219.20
Purchase #5	$11.40	10.358%	$12.5808	$12.58	$12.60	$12.60
Purchase #6	$86.60	10.236%	$95.4644	$95.46	$95.45	$95.50
Purchase #7	$10.90	4.128%	$11.35	$11.35	$11.35	$11.40
7 purchase totals =	$648.35		$694.1760	$694.17	$694.20	$694.20