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	$51.32	5.707%	$54.2488	$54.25	$54.25	$54.20
Purchase #2	$152.70	13.664%	$173.5649	$173.56	$173.55	$173.60
Purchase #3	$179.32	4.121%	$186.7098	$186.71	$186.70	$186.70
Purchase #4	$122.37	3.254%	$126.3519	$126.35	$126.35	$126.40
Purchase #5	$175.30	13.105%	$198.2731	$198.27	$198.25	$198.30
Purchase #6	$166.94	3.849%	$173.3655	$173.37	$173.35	$173.40
Purchase #7	$137.56	4.742%	$144.0831	$144.08	$144.10	$144.10
7 purchase totals =	$985.51		$1,056.5971	$1,056.59	$1,056.55	$1,056.70