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	$114.95	11.452%	$128.1141	$128.11	$128.10	$128.10
Purchase #2	$99.90	10.304%	$110.1937	$110.19	$110.20	$110.20
Purchase #3	$158.66	6.256%	$168.5858	$168.59	$168.60	$168.60
Purchase #4	$33.92	4.256%	$35.3636	$35.36	$35.35	$35.40
Purchase #5	$81.68	10.218%	$90.0261	$90.03	$90.05	$90.00
Purchase #6	$154.95	11.225%	$172.3431	$172.34	$172.35	$172.30
Purchase #7	$88.47	5.690%	$93.5039	$93.50	$93.50	$93.50
7 purchase totals =	$732.53		$798.1303	$798.12	$798.15	$798.10