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	$136.61	7.546%	$146.9186	$146.92	$146.90	$146.90
Purchase #2	$144.60	6.276%	$153.6751	$153.68	$153.70	$153.70
Purchase #3	$93.67	7.462%	$100.6597	$100.66	$100.65	$100.70
Purchase #4	$183.39	13.828%	$208.7492	$208.75	$208.75	$208.70
Purchase #5	$134.90	11.265%	$150.0965	$150.10	$150.10	$150.10
Purchase #6	$186.82	7.167%	$200.2094	$200.21	$200.20	$200.20
Purchase #7	$62.40	13.163%	$70.6137	$70.61	$70.60	$70.60
7 purchase totals =	$942.39		$1,030.9222	$1,030.93	$1,030.90	$1,030.90