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	$159.93	5.580%	$168.8541	$168.85	$168.85	$168.90
Purchase #2	$174.41	4.847%	$182.8637	$182.86	$182.85	$182.90
Purchase #3	$138.54	4.276%	$144.464	$144.46	$144.45	$144.50
Purchase #4	$11.87	4.852%	$12.4459	$12.45	$12.45	$12.40
Purchase #5	$159.35	13.325%	$180.5834	$180.58	$180.60	$180.60
Purchase #6	$43.43	5.605%	$45.8643	$45.86	$45.85	$45.90
Purchase #7	$28.26	13.374%	$32.0395	$32.04	$32.05	$32.00
7 purchase totals =	$715.79		$767.1149	$767.10	$767.10	$767.20