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	$128.90	10.479%	$142.4074	$142.41	$142.40	$142.40
Purchase #2	$52.29	8.532%	$56.7514	$56.75	$56.75	$56.80
Purchase #3	$206.84	10.685%	$228.9409	$228.94	$228.95	$228.90
Purchase #4	$225.80	13.139%	$255.4679	$255.47	$255.45	$255.50
Purchase #5	$176.83	11.395%	$196.9798	$196.98	$197.00	$197.00
Purchase #6	$10.57	8.127%	$11.429	$11.43	$11.45	$11.40
Purchase #7	$237.75	6.522%	$253.2561	$253.26	$253.25	$253.30
7 purchase totals =	$1,038.98		$1,145.2325	$1,145.24	$1,145.25	$1,145.30