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	$35.61	8.372%	$38.5913	$38.59	$38.60	$38.60
Purchase #2	$90.33	6.195%	$95.9259	$95.93	$95.95	$95.90
Purchase #3	$5.91	6.365%	$6.2862	$6.29	$6.30	$6.30
Purchase #4	$82.35	9.311%	$90.0176	$90.02	$90.00	$90.00
Purchase #5	$133.74	10.497%	$147.7787	$147.78	$147.80	$147.80
Purchase #6	$100.91	7.643%	$108.6226	$108.62	$108.60	$108.60
Purchase #7	$218.77	7.540%	$235.2653	$235.27	$235.25	$235.30
7 purchase totals =	$667.62		$722.4876	$722.50	$722.50	$722.50