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	$173.92	12.858%	$196.2826	$196.28	$196.30	$196.30
Purchase #2	$162.73	9.860%	$178.7752	$178.78	$178.80	$178.80
Purchase #3	$240.85	10.685%	$266.5848	$266.58	$266.60	$266.60
Purchase #4	$97.73	6.794%	$104.3698	$104.37	$104.35	$104.40
Purchase #5	$137.74	3.440%	$142.4783	$142.48	$142.50	$142.50
Purchase #6	$173.66	11.472%	$193.5823	$193.58	$193.60	$193.60
Purchase #7	$126.38	6.496%	$134.5896	$134.59	$134.60	$134.60
7 purchase totals =	$1,113.01		$1,216.6626	$1,216.66	$1,216.75	$1,216.80