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	$126.39	3.270%	$130.523	$130.52	$130.50	$130.50
Purchase #2	$38.64	5.795%	$40.8792	$40.88	$40.90	$40.90
Purchase #3	$139.45	4.428%	$145.6248	$145.62	$145.60	$145.60
Purchase #4	$64.73	4.761%	$67.8118	$67.81	$67.80	$67.80
Purchase #5	$60.82	3.706%	$63.074	$63.07	$63.05	$63.10
Purchase #6	$67.34	10.853%	$74.6484	$74.65	$74.65	$74.60
Purchase #7	$71.53	10.338%	$78.9248	$78.92	$78.90	$78.90
7 purchase totals =	$568.90		$601.4860	$601.47	$601.40	$601.40