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	$219.59	7.848%	$236.8234	$236.82	$236.80	$236.80
Purchase #2	$243.83	10.425%	$269.2493	$269.25	$269.25	$269.20
Purchase #3	$98.86	13.624%	$112.3287	$112.33	$112.35	$112.30
Purchase #4	$20.60	5.193%	$21.6698	$21.67	$21.65	$21.70
Purchase #5	$31.48	6.602%	$33.5583	$33.56	$33.55	$33.60
Purchase #6	$134.70	13.768%	$153.2455	$153.25	$153.25	$153.20
Purchase #7	$194.54	8.769%	$211.5992	$211.60	$211.60	$211.60
7 purchase totals =	$943.60		$1,038.4742	$1,038.48	$1,038.45	$1,038.40