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	$173.84	7.232%	$186.4121	$186.41	$186.40	$186.40
Purchase #2	$117.96	3.157%	$121.684	$121.68	$121.70	$121.70
Purchase #3	$221.55	5.437%	$233.5957	$233.60	$233.60	$233.60
Purchase #4	$154.50	11.650%	$172.4993	$172.50	$172.50	$172.50
Purchase #5	$54.96	8.291%	$59.5167	$59.52	$59.50	$59.50
Purchase #6	$150.32	10.222%	$165.6857	$165.69	$165.70	$165.70
Purchase #7	$172.28	5.217%	$181.2678	$181.27	$181.25	$181.30
7 purchase totals =	$1,045.41		$1,120.6613	$1,120.67	$1,120.65	$1,120.70