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	$103.39	7.861%	$111.5175	$111.52	$111.50	$111.50
Purchase #2	$56.83	5.191%	$59.78	$59.78	$59.80	$59.80
Purchase #3	$14.51	5.423%	$15.2969	$15.30	$15.30	$15.30
Purchase #4	$85.89	8.711%	$93.3719	$93.37	$93.35	$93.40
Purchase #5	$78.86	3.489%	$81.6114	$81.61	$81.60	$81.60
Purchase #6	$106.45	4.403%	$111.137	$111.14	$111.15	$111.10
Purchase #7	$142.82	12.664%	$160.9067	$160.91	$160.90	$160.90
7 purchase totals =	$588.75		$633.6214	$633.63	$633.60	$633.60