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	$121.38	4.827%	$127.239	$127.24	$127.25	$127.20
Purchase #2	$52.26	10.570%	$57.7839	$57.78	$57.80	$57.80
Purchase #3	$51.92	6.799%	$55.45	$55.45	$55.45	$55.50
Purchase #4	$95.47	13.608%	$108.4616	$108.46	$108.45	$108.50
Purchase #5	$206.96	13.493%	$234.8851	$234.89	$234.90	$234.90
Purchase #6	$64.59	5.251%	$67.9816	$67.98	$68.00	$68.00
Purchase #7	$60.51	3.650%	$62.7186	$62.72	$62.70	$62.70
7 purchase totals =	$653.09		$714.5198	$714.52	$714.55	$714.60