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	$54.67	9.716%	$59.9817	$59.98	$60.00	$60.00
Purchase #2	$173.94	7.570%	$187.1073	$187.11	$187.10	$187.10
Purchase #3	$126.54	13.734%	$143.919	$143.92	$143.90	$143.90
Purchase #4	$30.82	7.130%	$33.0175	$33.02	$33.00	$33.00
Purchase #5	$66.75	7.467%	$71.7342	$71.73	$71.75	$71.70
Purchase #6	$161.71	6.773%	$172.6626	$172.66	$172.65	$172.70
Purchase #7	$89.47	7.372%	$96.0657	$96.07	$96.05	$96.10
7 purchase totals =	$703.90		$764.4880	$764.49	$764.45	$764.50