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	$7.52	4.147%	$7.8319	$7.83	$7.85	$7.80
Purchase #2	$17.69	9.490%	$19.3688	$19.37	$19.35	$19.40
Purchase #3	$137.86	3.122%	$142.164	$142.16	$142.15	$142.20
Purchase #4	$199.88	11.790%	$223.4459	$223.45	$223.45	$223.40
Purchase #5	$104.50	11.799%	$116.83	$116.83	$116.85	$116.80
Purchase #6	$172.39	13.832%	$196.235	$196.24	$196.25	$196.20
Purchase #7	$44.28	13.365%	$50.198	$50.20	$50.20	$50.20
7 purchase totals =	$684.12		$756.0736	$756.08	$756.10	$756.00