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	$161.83	10.729%	$179.1927	$179.19	$179.20	$179.20
Purchase #2	$234.82	10.457%	$259.3751	$259.38	$259.40	$259.40
Purchase #3	$208.77	11.653%	$233.098	$233.10	$233.10	$233.10
Purchase #4	$158.57	8.835%	$172.5797	$172.58	$172.60	$172.60
Purchase #5	$197.89	3.174%	$204.171	$204.17	$204.15	$204.20
Purchase #6	$156.37	8.265%	$169.294	$169.29	$169.30	$169.30
Purchase #7	$213.53	13.127%	$241.5601	$241.56	$241.55	$241.60
7 purchase totals =	$1,331.78		$1,459.2706	$1,459.27	$1,459.30	$1,459.40