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	$208.29	5.859%	$220.4937	$220.49	$220.50	$220.50
Purchase #2	$17.35	8.563%	$18.8357	$18.84	$18.85	$18.80
Purchase #3	$137.99	3.528%	$142.8583	$142.86	$142.85	$142.90
Purchase #4	$52.91	6.443%	$56.319	$56.32	$56.30	$56.30
Purchase #5	$141.61	6.200%	$150.3898	$150.39	$150.40	$150.40
Purchase #6	$11.83	4.134%	$12.3191	$12.32	$12.30	$12.30
Purchase #7	$81.42	6.346%	$86.5869	$86.59	$86.60	$86.60
7 purchase totals =	$651.40		$687.8025	$687.81	$687.80	$687.80