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	$137.63	12.401%	$154.6975	$154.70	$154.70	$154.70
Purchase #2	$48.32	13.659%	$54.92	$54.92	$54.90	$54.90
Purchase #3	$96.56	9.585%	$105.8153	$105.82	$105.80	$105.80
Purchase #4	$214.73	9.375%	$234.8609	$234.86	$234.85	$234.90
Purchase #5	$219.28	9.861%	$240.9032	$240.90	$240.90	$240.90
Purchase #6	$248.56	3.563%	$257.4162	$257.42	$257.40	$257.40
Purchase #7	$113.62	12.241%	$127.5282	$127.53	$127.55	$127.50
7 purchase totals =	$1,078.70		$1,176.1413	$1,176.15	$1,176.10	$1,176.10