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	$21.67	12.850%	$24.4546	$24.45	$24.45	$24.50
Purchase #2	$45.92	13.811%	$52.262	$52.26	$52.25	$52.30
Purchase #3	$74.78	3.397%	$77.3203	$77.32	$77.30	$77.30
Purchase #4	$169.34	7.720%	$182.413	$182.41	$182.40	$182.40
Purchase #5	$86.64	3.482%	$89.6568	$89.66	$89.65	$89.70
Purchase #6	$233.92	9.395%	$255.8968	$255.90	$255.90	$255.90
Purchase #7	$72.77	3.688%	$75.4538	$75.45	$75.45	$75.50
7 purchase totals =	$705.04		$757.4573	$757.45	$757.40	$757.60