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	$99.82	12.794%	$112.591	$112.59	$112.60	$112.60
Purchase #2	$7.58	10.860%	$8.4032	$8.40	$8.40	$8.40
Purchase #3	$153.69	12.538%	$172.9597	$172.96	$172.95	$173.00
Purchase #4	$153.86	9.171%	$167.9705	$167.97	$167.95	$168.00
Purchase #5	$184.60	13.784%	$210.0453	$210.05	$210.05	$210.00
Purchase #6	$49.43	11.609%	$55.1683	$55.17	$55.15	$55.20
Purchase #7	$111.73	4.609%	$116.8796	$116.88	$116.90	$116.90
7 purchase totals =	$760.71		$844.0176	$844.02	$844.00	$844.10