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	$144.77	11.227%	$161.0233	$161.02	$161.00	$161.00
Purchase #2	$191.39	12.375%	$215.0745	$215.07	$215.05	$215.10
Purchase #3	$107.51	3.797%	$111.5922	$111.59	$111.60	$111.60
Purchase #4	$204.33	11.320%	$227.4602	$227.46	$227.45	$227.50
Purchase #5	$48.51	3.754%	$50.3311	$50.33	$50.35	$50.30
Purchase #6	$105.78	13.504%	$120.0645	$120.06	$120.05	$120.10
Purchase #7	$93.38	12.406%	$104.9647	$104.96	$104.95	$105.00
7 purchase totals =	$895.67		$990.5105	$990.49	$990.45	$990.60