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	$141.29	9.622%	$154.8849	$154.88	$154.90	$154.90
Purchase #2	$175.47	3.184%	$181.057	$181.06	$181.05	$181.10
Purchase #3	$39.80	3.604%	$41.2344	$41.23	$41.25	$41.20
Purchase #4	$241.59	5.816%	$255.6409	$255.64	$255.65	$255.60
Purchase #5	$129.56	11.530%	$144.4983	$144.50	$144.50	$144.50
Purchase #6	$102.72	13.447%	$116.5328	$116.53	$116.55	$116.50
Purchase #7	$229.28	8.725%	$249.2847	$249.28	$249.30	$249.30
7 purchase totals =	$1,059.71		$1,143.1330	$1,143.12	$1,143.20	$1,143.10