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	$47.86	12.562%	$53.8722	$53.87	$53.85	$53.90
Purchase #2	$21.75	13.834%	$24.7589	$24.76	$24.75	$24.80
Purchase #3	$79.90	13.613%	$90.7768	$90.78	$90.80	$90.80
Purchase #4	$66.87	13.481%	$75.8847	$75.88	$75.90	$75.90
Purchase #5	$179.95	9.216%	$196.5342	$196.53	$196.55	$196.50
Purchase #6	$178.38	3.362%	$184.3771	$184.38	$184.40	$184.40
Purchase #7	$226.56	5.476%	$238.9664	$238.97	$238.95	$239.00
7 purchase totals =	$801.27		$865.1703	$865.17	$865.20	$865.30