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	$103.66	7.838%	$111.7849	$111.78	$111.80	$111.80
Purchase #2	$145.45	11.846%	$162.68	$162.68	$162.70	$162.70
Purchase #3	$239.60	9.554%	$262.4914	$262.49	$262.50	$262.50
Purchase #4	$137.28	7.511%	$147.5911	$147.59	$147.60	$147.60
Purchase #5	$70.43	3.107%	$72.6183	$72.62	$72.60	$72.60
Purchase #6	$112.74	3.412%	$116.5867	$116.59	$116.60	$116.60
Purchase #7	$81.28	9.357%	$88.8854	$88.89	$88.90	$88.90
7 purchase totals =	$890.44		$962.6378	$962.64	$962.70	$962.70