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	$140.36	3.203%	$144.8557	$144.86	$144.85	$144.90
Purchase #2	$12.92	4.631%	$13.5183	$13.52	$13.50	$13.50
Purchase #3	$94.51	6.229%	$100.397	$100.40	$100.40	$100.40
Purchase #4	$149.35	7.717%	$160.8753	$160.88	$160.90	$160.90
Purchase #5	$230.75	4.552%	$241.2537	$241.25	$241.25	$241.30
Purchase #6	$152.74	7.768%	$164.6048	$164.60	$164.60	$164.60
Purchase #7	$13.98	7.403%	$15.0149	$15.01	$15.00	$15.00
7 purchase totals =	$794.61		$840.5197	$840.52	$840.50	$840.60