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	$111.69	5.762%	$118.1256	$118.13	$118.15	$118.10
Purchase #2	$5.80	13.618%	$6.5898	$6.59	$6.60	$6.60
Purchase #3	$23.83	3.194%	$24.5911	$24.59	$24.60	$24.60
Purchase #4	$157.68	9.139%	$172.0904	$172.09	$172.10	$172.10
Purchase #5	$26.37	8.308%	$28.5608	$28.56	$28.55	$28.60
Purchase #6	$139.42	9.761%	$153.0288	$153.03	$153.05	$153.00
Purchase #7	$31.42	11.732%	$35.1062	$35.11	$35.10	$35.10
7 purchase totals =	$496.21		$538.0927	$538.10	$538.15	$538.10