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	$148.30	11.675%	$165.614	$165.61	$165.60	$165.60
Purchase #2	$141.71	4.743%	$148.4313	$148.43	$148.45	$148.40
Purchase #3	$103.59	6.268%	$110.083	$110.08	$110.10	$110.10
Purchase #4	$100.55	10.712%	$111.3209	$111.32	$111.30	$111.30
Purchase #5	$61.89	6.680%	$66.0243	$66.02	$66.00	$66.00
Purchase #6	$154.81	4.860%	$162.3338	$162.33	$162.35	$162.30
Purchase #7	$16.92	11.654%	$18.8919	$18.89	$18.90	$18.90
7 purchase totals =	$727.77		$782.6992	$782.68	$782.70	$782.60