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	$69.80	3.342%	$72.1327	$72.13	$72.15	$72.10
Purchase #2	$154.71	13.406%	$175.4504	$175.45	$175.45	$175.50
Purchase #3	$240.33	4.382%	$250.8613	$250.86	$250.85	$250.90
Purchase #4	$145.85	9.462%	$159.6503	$159.65	$159.65	$159.70
Purchase #5	$172.37	5.577%	$181.9831	$181.98	$182.00	$182.00
Purchase #6	$159.89	7.355%	$171.6499	$171.65	$171.65	$171.60
Purchase #7	$48.52	13.103%	$54.8776	$54.88	$54.90	$54.90
7 purchase totals =	$991.47		$1,066.6053	$1,066.60	$1,066.65	$1,066.70