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	$146.63	10.713%	$162.3385	$162.34	$162.35	$162.30
Purchase #2	$114.99	12.162%	$128.9751	$128.98	$129.00	$129.00
Purchase #3	$94.72	6.320%	$100.7063	$100.71	$100.70	$100.70
Purchase #4	$95.27	3.176%	$98.2958	$98.30	$98.30	$98.30
Purchase #5	$139.86	10.707%	$154.8348	$154.83	$154.85	$154.80
Purchase #6	$190.59	7.363%	$204.6231	$204.62	$204.60	$204.60
Purchase #7	$57.28	7.368%	$61.5004	$61.50	$61.50	$61.50
7 purchase totals =	$839.34		$911.2740	$911.28	$911.30	$911.20