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	$215.97	5.363%	$227.5525	$227.55	$227.55	$227.60
Purchase #2	$52.58	11.112%	$58.4227	$58.42	$58.40	$58.40
Purchase #3	$48.25	12.630%	$54.344	$54.34	$54.35	$54.30
Purchase #4	$105.83	5.298%	$111.4369	$111.44	$111.45	$111.40
Purchase #5	$100.41	13.176%	$113.64	$113.64	$113.65	$113.60
Purchase #6	$113.98	5.168%	$119.8705	$119.87	$119.85	$119.90
Purchase #7	$12.75	8.527%	$13.8372	$13.84	$13.85	$13.80
7 purchase totals =	$649.77		$699.1038	$699.10	$699.10	$699.00