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	$101.36	9.597%	$111.0875	$111.09	$111.10	$111.10
Purchase #2	$18.71	12.163%	$20.9857	$20.99	$21.00	$21.00
Purchase #3	$7.90	3.730%	$8.1947	$8.19	$8.20	$8.20
Purchase #4	$29.42	10.466%	$32.4991	$32.50	$32.50	$32.50
Purchase #5	$195.64	12.340%	$219.782	$219.78	$219.80	$219.80
Purchase #6	$55.68	6.679%	$59.3989	$59.40	$59.40	$59.40
Purchase #7	$29.43	6.603%	$31.3733	$31.37	$31.35	$31.40
7 purchase totals =	$438.14		$483.3212	$483.32	$483.35	$483.40