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	$216.98	9.867%	$238.3894	$238.39	$238.40	$238.40
Purchase #2	$186.56	4.151%	$194.3041	$194.30	$194.30	$194.30
Purchase #3	$125.76	8.610%	$136.5879	$136.59	$136.60	$136.60
Purchase #4	$107.33	9.309%	$117.3213	$117.32	$117.30	$117.30
Purchase #5	$42.59	3.173%	$43.9414	$43.94	$43.95	$43.90
Purchase #6	$158.51	7.738%	$170.7755	$170.78	$170.80	$170.80
Purchase #7	$159.68	10.778%	$176.8903	$176.89	$176.90	$176.90
7 purchase totals =	$997.41		$1,078.2099	$1,078.21	$1,078.25	$1,078.20