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	$113.51	8.570%	$123.2378	$123.24	$123.25	$123.20
Purchase #2	$235.85	8.638%	$256.2227	$256.22	$256.20	$256.20
Purchase #3	$46.69	5.513%	$49.264	$49.26	$49.25	$49.30
Purchase #4	$101.74	4.641%	$106.4618	$106.46	$106.45	$106.50
Purchase #5	$77.39	3.585%	$80.1644	$80.16	$80.15	$80.20
Purchase #6	$103.77	7.184%	$111.2248	$111.22	$111.20	$111.20
Purchase #7	$126.35	3.874%	$131.2448	$131.24	$131.25	$131.20
7 purchase totals =	$805.30		$857.8203	$857.80	$857.75	$857.80