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	$55.92	10.393%	$61.7318	$61.73	$61.75	$61.70
Purchase #2	$93.43	7.443%	$100.384	$100.38	$100.40	$100.40
Purchase #3	$39.67	10.390%	$43.7917	$43.79	$43.80	$43.80
Purchase #4	$194.26	12.275%	$218.1054	$218.11	$218.10	$218.10
Purchase #5	$31.78	4.389%	$33.1748	$33.17	$33.15	$33.20
Purchase #6	$145.91	8.764%	$158.6976	$158.70	$158.70	$158.70
Purchase #7	$94.61	9.825%	$103.9054	$103.91	$103.90	$103.90
7 purchase totals =	$655.58		$719.7907	$719.79	$719.80	$719.80