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	$82.90	7.677%	$89.2642	$89.26	$89.25	$89.30
Purchase #2	$12.71	7.725%	$13.6918	$13.69	$13.70	$13.70
Purchase #3	$109.65	12.553%	$123.4144	$123.41	$123.40	$123.40
Purchase #4	$88.36	8.615%	$95.9722	$95.97	$95.95	$96.00
Purchase #5	$99.25	11.442%	$110.6062	$110.61	$110.60	$110.60
Purchase #6	$97.32	10.822%	$107.852	$107.85	$107.85	$107.90
Purchase #7	$76.68	6.280%	$81.4955	$81.50	$81.50	$81.50
7 purchase totals =	$566.87		$622.2963	$622.29	$622.25	$622.40