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	$107.71	8.846%	$117.238	$117.24	$117.25	$117.20
Purchase #2	$164.76	7.124%	$176.4975	$176.50	$176.50	$176.50
Purchase #3	$75.45	4.610%	$78.9282	$78.93	$78.95	$78.90
Purchase #4	$69.50	13.291%	$78.7372	$78.74	$78.75	$78.70
Purchase #5	$147.38	11.671%	$164.5807	$164.58	$164.60	$164.60
Purchase #6	$170.35	10.686%	$188.5536	$188.55	$188.55	$188.60
Purchase #7	$210.35	12.485%	$236.6122	$236.61	$236.60	$236.60
7 purchase totals =	$945.50		$1,041.1474	$1,041.15	$1,041.20	$1,041.10