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	$61.32	6.551%	$65.3371	$65.34	$65.35	$65.30
Purchase #2	$86.30	13.556%	$97.9988	$98.00	$98.00	$98.00
Purchase #3	$190.64	7.564%	$205.06	$205.06	$205.05	$205.10
Purchase #4	$221.34	5.510%	$233.5358	$233.54	$233.55	$233.50
Purchase #5	$47.73	13.378%	$54.1153	$54.12	$54.10	$54.10
Purchase #6	$238.67	13.189%	$270.1482	$270.15	$270.15	$270.10
Purchase #7	$132.27	8.849%	$143.9746	$143.97	$143.95	$144.00
7 purchase totals =	$978.27		$1,070.1698	$1,070.18	$1,070.15	$1,070.10