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	$107.33	4.699%	$112.3734	$112.37	$112.35	$112.40
Purchase #2	$155.85	10.601%	$172.3717	$172.37	$172.35	$172.40
Purchase #3	$227.27	11.662%	$253.7742	$253.77	$253.75	$253.80
Purchase #4	$132.72	9.209%	$144.9422	$144.94	$144.95	$144.90
Purchase #5	$178.43	11.484%	$198.9209	$198.92	$198.90	$198.90
Purchase #6	$233.34	4.398%	$243.6023	$243.60	$243.60	$243.60
Purchase #7	$204.59	3.339%	$211.4213	$211.42	$211.40	$211.40
7 purchase totals =	$1,239.53		$1,337.4060	$1,337.39	$1,337.30	$1,337.40