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	$233.91	9.293%	$255.6473	$255.65	$255.65	$255.60
Purchase #2	$140.32	9.390%	$153.496	$153.50	$153.50	$153.50
Purchase #3	$81.65	9.869%	$89.708	$89.71	$89.70	$89.70
Purchase #4	$42.26	12.565%	$47.57	$47.57	$47.55	$47.60
Purchase #5	$196.38	4.873%	$205.9496	$205.95	$205.95	$205.90
Purchase #6	$18.46	12.727%	$20.8094	$20.81	$20.80	$20.80
Purchase #7	$241.43	5.683%	$255.1505	$255.15	$255.15	$255.20
7 purchase totals =	$954.41		$1,028.3308	$1,028.34	$1,028.30	$1,028.30