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	$211.26	11.402%	$235.3479	$235.35	$235.35	$235.30
Purchase #2	$171.34	3.796%	$177.8441	$177.84	$177.85	$177.80
Purchase #3	$249.98	4.206%	$260.4942	$260.49	$260.50	$260.50
Purchase #4	$100.25	11.105%	$111.3828	$111.38	$111.40	$111.40
Purchase #5	$205.64	7.693%	$221.4599	$221.46	$221.45	$221.50
Purchase #6	$77.32	9.281%	$84.4961	$84.50	$84.50	$84.50
Purchase #7	$59.26	4.390%	$61.8615	$61.86	$61.85	$61.90
7 purchase totals =	$1,075.05		$1,152.8865	$1,152.88	$1,152.90	$1,152.90