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	$184.77	6.361%	$196.5232	$196.52	$196.50	$196.50
Purchase #2	$17.48	4.808%	$18.3204	$18.32	$18.30	$18.30
Purchase #3	$96.95	6.773%	$103.5164	$103.52	$103.50	$103.50
Purchase #4	$219.44	12.547%	$246.9731	$246.97	$246.95	$247.00
Purchase #5	$16.58	6.634%	$17.6799	$17.68	$17.70	$17.70
Purchase #6	$72.25	8.450%	$78.3551	$78.36	$78.35	$78.40
Purchase #7	$113.88	5.564%	$120.2163	$120.22	$120.20	$120.20
7 purchase totals =	$721.35		$781.5844	$781.59	$781.50	$781.60