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	$145.76	10.420%	$160.9482	$160.95	$160.95	$160.90
Purchase #2	$62.83	8.573%	$68.2164	$68.22	$68.20	$68.20
Purchase #3	$40.59	4.752%	$42.5188	$42.52	$42.50	$42.50
Purchase #4	$163.71	7.664%	$176.2567	$176.26	$176.25	$176.30
Purchase #5	$59.25	4.871%	$62.1361	$62.14	$62.15	$62.10
Purchase #6	$81.55	11.727%	$91.1134	$91.11	$91.10	$91.10
Purchase #7	$78.35	6.311%	$83.2947	$83.29	$83.30	$83.30
7 purchase totals =	$632.04		$684.4843	$684.49	$684.45	$684.40