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	$90.51	6.219%	$96.1388	$96.14	$96.15	$96.10
Purchase #2	$54.86	10.679%	$60.7185	$60.72	$60.70	$60.70
Purchase #3	$122.66	9.391%	$134.179	$134.18	$134.20	$134.20
Purchase #4	$91.89	9.687%	$100.7914	$100.79	$100.80	$100.80
Purchase #5	$94.68	6.185%	$100.536	$100.54	$100.55	$100.50
Purchase #6	$40.58	13.576%	$46.0891	$46.09	$46.10	$46.10
Purchase #7	$82.87	4.869%	$86.9049	$86.90	$86.90	$86.90
7 purchase totals =	$578.05		$625.3577	$625.36	$625.40	$625.30