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	$111.28	5.466%	$117.3626	$117.36	$117.35	$117.40
Purchase #2	$215.53	4.368%	$224.9444	$224.94	$224.95	$224.90
Purchase #3	$103.77	9.164%	$113.2795	$113.28	$113.30	$113.30
Purchase #4	$128.30	4.577%	$134.1723	$134.17	$134.15	$134.20
Purchase #5	$248.77	6.498%	$264.9351	$264.94	$264.95	$264.90
Purchase #6	$72.99	13.609%	$82.9232	$82.92	$82.90	$82.90
Purchase #7	$88.71	8.527%	$96.2743	$96.27	$96.25	$96.30
7 purchase totals =	$969.35		$1,033.8914	$1,033.88	$1,033.85	$1,033.90