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	$246.88	3.545%	$255.6319	$255.63	$255.65	$255.60
Purchase #2	$57.44	12.363%	$64.5413	$64.54	$64.55	$64.50
Purchase #3	$85.35	13.277%	$96.6819	$96.68	$96.70	$96.70
Purchase #4	$214.83	5.844%	$227.3847	$227.38	$227.40	$227.40
Purchase #5	$78.42	10.778%	$86.8721	$86.87	$86.85	$86.90
Purchase #6	$142.39	7.160%	$152.5851	$152.59	$152.60	$152.60
Purchase #7	$241.89	12.306%	$271.657	$271.66	$271.65	$271.70
7 purchase totals =	$1,067.20		$1,155.3540	$1,155.35	$1,155.40	$1,155.40