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	$138.50	7.344%	$148.6714	$148.67	$148.65	$148.70
Purchase #2	$155.36	8.149%	$168.0203	$168.02	$168.00	$168.00
Purchase #3	$155.94	7.588%	$167.7727	$167.77	$167.75	$167.80
Purchase #4	$168.99	7.526%	$181.7082	$181.71	$181.70	$181.70
Purchase #5	$86.52	3.860%	$89.8597	$89.86	$89.85	$89.90
Purchase #6	$233.40	7.658%	$251.2738	$251.27	$251.25	$251.30
Purchase #7	$175.92	3.215%	$181.5758	$181.58	$181.60	$181.60
7 purchase totals =	$1,114.63		$1,188.8819	$1,188.88	$1,188.80	$1,189.00