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	$176.90	3.622%	$183.3073	$183.31	$183.30	$183.30
Purchase #2	$241.39	5.343%	$254.2875	$254.29	$254.30	$254.30
Purchase #3	$141.68	10.569%	$156.6542	$156.65	$156.65	$156.70
Purchase #4	$51.70	6.855%	$55.244	$55.24	$55.25	$55.20
Purchase #5	$178.66	12.190%	$200.4387	$200.44	$200.45	$200.40
Purchase #6	$135.89	11.406%	$151.3896	$151.39	$151.40	$151.40
Purchase #7	$170.37	4.798%	$178.5444	$178.54	$178.55	$178.50
7 purchase totals =	$1,096.59		$1,179.8657	$1,179.86	$1,179.90	$1,179.80