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	$196.39	6.818%	$209.7799	$209.78	$209.80	$209.80
Purchase #2	$108.59	10.369%	$119.8497	$119.85	$119.85	$119.80
Purchase #3	$172.86	12.400%	$194.2946	$194.29	$194.30	$194.30
Purchase #4	$185.32	8.151%	$200.4254	$200.43	$200.45	$200.40
Purchase #5	$132.95	8.364%	$144.0699	$144.07	$144.05	$144.10
Purchase #6	$139.97	6.757%	$149.4278	$149.43	$149.45	$149.40
Purchase #7	$66.81	10.823%	$74.0408	$74.04	$74.05	$74.00
7 purchase totals =	$1,002.89		$1,091.8881	$1,091.89	$1,091.95	$1,091.80