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	$134.59	7.472%	$144.6466	$144.65	$144.65	$144.60
Purchase #2	$111.77	13.388%	$126.7338	$126.73	$126.75	$126.70
Purchase #3	$227.27	12.104%	$254.7788	$254.78	$254.80	$254.80
Purchase #4	$84.52	11.336%	$94.1012	$94.10	$94.10	$94.10
Purchase #5	$68.35	5.770%	$72.2938	$72.29	$72.30	$72.30
Purchase #6	$177.62	5.472%	$187.3394	$187.34	$187.35	$187.30
Purchase #7	$50.39	4.398%	$52.6062	$52.61	$52.60	$52.60
7 purchase totals =	$854.51		$932.4998	$932.50	$932.55	$932.40