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	$35.88	3.848%	$37.2607	$37.26	$37.25	$37.30
Purchase #2	$108.98	7.278%	$116.9116	$116.91	$116.90	$116.90
Purchase #3	$185.71	7.469%	$199.5807	$199.58	$199.60	$199.60
Purchase #4	$165.56	13.573%	$188.0315	$188.03	$188.05	$188.00
Purchase #5	$37.34	11.623%	$41.68	$41.68	$41.70	$41.70
Purchase #6	$28.68	13.637%	$32.5911	$32.59	$32.60	$32.60
Purchase #7	$134.35	10.707%	$148.7349	$148.73	$148.75	$148.70
7 purchase totals =	$696.50		$764.7905	$764.78	$764.85	$764.80