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	$58.65	4.523%	$61.3027	$61.30	$61.30	$61.30
Purchase #2	$230.79	11.307%	$256.8854	$256.89	$256.90	$256.90
Purchase #3	$88.87	13.456%	$100.8283	$100.83	$100.85	$100.80
Purchase #4	$9.74	5.127%	$10.2394	$10.24	$10.25	$10.20
Purchase #5	$43.91	3.673%	$45.5228	$45.52	$45.50	$45.50
Purchase #6	$187.82	10.419%	$207.389	$207.39	$207.40	$207.40
Purchase #7	$224.30	8.629%	$243.6548	$243.65	$243.65	$243.70
7 purchase totals =	$844.08		$925.8224	$925.82	$925.85	$925.80