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	$164.53	8.426%	$178.3933	$178.39	$178.40	$178.40
Purchase #2	$79.54	3.102%	$82.0073	$82.01	$82.00	$82.00
Purchase #3	$21.42	5.563%	$22.6116	$22.61	$22.60	$22.60
Purchase #4	$105.31	13.661%	$119.6964	$119.70	$119.70	$119.70
Purchase #5	$19.91	6.614%	$21.2268	$21.23	$21.25	$21.20
Purchase #6	$31.25	13.168%	$35.365	$35.37	$35.35	$35.40
Purchase #7	$110.74	5.457%	$116.7831	$116.78	$116.80	$116.80
7 purchase totals =	$532.70		$576.0835	$576.09	$576.10	$576.10