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	$240.60	5.109%	$252.8923	$252.89	$252.90	$252.90
Purchase #2	$117.70	3.203%	$121.4699	$121.47	$121.45	$121.50
Purchase #3	$207.49	12.828%	$234.1068	$234.11	$234.10	$234.10
Purchase #4	$177.76	3.325%	$183.6705	$183.67	$183.65	$183.70
Purchase #5	$61.43	3.604%	$63.6439	$63.64	$63.65	$63.60
Purchase #6	$137.25	5.340%	$144.5792	$144.58	$144.60	$144.60
Purchase #7	$184.28	6.641%	$196.518	$196.52	$196.50	$196.50
7 purchase totals =	$1,126.51		$1,196.8806	$1,196.88	$1,196.85	$1,196.90