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	$149.42	10.175%	$164.6235	$164.62	$164.60	$164.60
Purchase #2	$38.25	4.762%	$40.0715	$40.07	$40.05	$40.10
Purchase #3	$82.70	12.595%	$93.1161	$93.12	$93.10	$93.10
Purchase #4	$128.66	10.413%	$142.0574	$142.06	$142.05	$142.10
Purchase #5	$122.81	6.764%	$131.1169	$131.12	$131.10	$131.10
Purchase #6	$52.77	3.294%	$54.5082	$54.51	$54.50	$54.50
Purchase #7	$145.43	6.399%	$154.7361	$154.74	$154.75	$154.70
7 purchase totals =	$720.04		$780.2297	$780.24	$780.15	$780.20