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	$58.78	9.527%	$64.38	$64.38	$64.40	$64.40
Purchase #2	$126.45	6.139%	$134.2128	$134.21	$134.20	$134.20
Purchase #3	$73.49	7.516%	$79.0135	$79.01	$79.00	$79.00
Purchase #4	$118.91	11.740%	$132.87	$132.87	$132.85	$132.90
Purchase #5	$111.51	10.675%	$123.4137	$123.41	$123.40	$123.40
Purchase #6	$90.29	5.655%	$95.3959	$95.40	$95.40	$95.40
Purchase #7	$107.28	6.836%	$114.6137	$114.61	$114.60	$114.60
7 purchase totals =	$686.71		$743.8996	$743.89	$743.85	$743.90