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	$182.39	10.575%	$201.6777	$201.68	$201.70	$201.70
Purchase #2	$95.33	5.440%	$100.516	$100.52	$100.50	$100.50
Purchase #3	$100.93	3.620%	$104.5837	$104.58	$104.60	$104.60
Purchase #4	$189.54	11.872%	$212.0422	$212.04	$212.05	$212.00
Purchase #5	$39.28	7.667%	$42.2916	$42.29	$42.30	$42.30
Purchase #6	$16.89	9.510%	$18.4962	$18.50	$18.50	$18.50
Purchase #7	$211.72	9.322%	$231.4565	$231.46	$231.45	$231.50
7 purchase totals =	$836.08		$911.0639	$911.07	$911.10	$911.10