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	$96.51	4.249%	$100.6107	$100.61	$100.60	$100.60
Purchase #2	$41.65	11.143%	$46.2911	$46.29	$46.30	$46.30
Purchase #3	$187.59	6.739%	$200.2317	$200.23	$200.25	$200.20
Purchase #4	$192.94	11.585%	$215.2921	$215.29	$215.30	$215.30
Purchase #5	$132.82	6.561%	$141.5343	$141.53	$141.55	$141.50
Purchase #6	$225.75	4.804%	$236.595	$236.60	$236.60	$236.60
Purchase #7	$48.75	12.401%	$54.7955	$54.80	$54.80	$54.80
7 purchase totals =	$926.01		$995.3504	$995.35	$995.40	$995.30