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	$249.28	4.335%	$260.0863	$260.09	$260.10	$260.10
Purchase #2	$91.90	8.546%	$99.7538	$99.75	$99.75	$99.80
Purchase #3	$106.96	3.872%	$111.1015	$111.10	$111.10	$111.10
Purchase #4	$136.29	4.297%	$142.1464	$142.15	$142.15	$142.10
Purchase #5	$108.43	11.657%	$121.0697	$121.07	$121.05	$121.10
Purchase #6	$95.78	4.674%	$100.2568	$100.26	$100.25	$100.30
Purchase #7	$153.46	13.777%	$174.6022	$174.60	$174.60	$174.60
7 purchase totals =	$942.10		$1,009.0167	$1,009.02	$1,009.00	$1,009.10