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	$38.93	7.422%	$41.8194	$41.82	$41.80	$41.80
Purchase #2	$186.57	5.114%	$196.1112	$196.11	$196.10	$196.10
Purchase #3	$123.84	11.317%	$137.855	$137.86	$137.85	$137.90
Purchase #4	$137.27	13.160%	$155.3347	$155.33	$155.35	$155.30
Purchase #5	$184.39	5.485%	$194.5038	$194.50	$194.50	$194.50
Purchase #6	$233.77	4.413%	$244.0863	$244.09	$244.10	$244.10
Purchase #7	$80.81	4.707%	$84.6137	$84.61	$84.60	$84.60
7 purchase totals =	$985.58		$1,054.3241	$1,054.32	$1,054.30	$1,054.30