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	$213.50	3.310%	$220.5669	$220.57	$220.55	$220.60
Purchase #2	$176.92	10.149%	$194.8756	$194.88	$194.90	$194.90
Purchase #3	$42.32	9.629%	$46.395	$46.40	$46.40	$46.40
Purchase #4	$58.86	4.691%	$61.6211	$61.62	$61.60	$61.60
Purchase #5	$75.91	6.482%	$80.8305	$80.83	$80.85	$80.80
Purchase #6	$78.39	3.848%	$81.4064	$81.41	$81.40	$81.40
Purchase #7	$38.82	12.867%	$43.815	$43.82	$43.80	$43.80
7 purchase totals =	$684.72		$729.5105	$729.53	$729.50	$729.50