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	$231.86	9.333%	$253.4995	$253.50	$253.50	$253.50
Purchase #2	$160.59	7.319%	$172.3436	$172.34	$172.35	$172.30
Purchase #3	$137.62	12.343%	$154.6064	$154.61	$154.60	$154.60
Purchase #4	$219.87	4.252%	$229.2189	$229.22	$229.20	$229.20
Purchase #5	$225.85	6.608%	$240.7742	$240.77	$240.75	$240.80
Purchase #6	$181.53	3.777%	$188.3864	$188.39	$188.40	$188.40
Purchase #7	$43.49	12.349%	$48.8606	$48.86	$48.85	$48.90
7 purchase totals =	$1,200.81		$1,287.6896	$1,287.69	$1,287.65	$1,287.70