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	$161.36	8.357%	$174.8449	$174.84	$174.85	$174.80
Purchase #2	$85.83	10.145%	$94.5375	$94.54	$94.55	$94.50
Purchase #3	$100.60	8.624%	$109.2757	$109.28	$109.30	$109.30
Purchase #4	$148.27	9.715%	$162.6744	$162.67	$162.65	$162.70
Purchase #5	$195.64	9.661%	$214.5408	$214.54	$214.55	$214.50
Purchase #6	$97.35	3.354%	$100.6151	$100.62	$100.60	$100.60
Purchase #7	$230.97	11.742%	$258.0905	$258.09	$258.10	$258.10
7 purchase totals =	$1,020.02		$1,114.5789	$1,114.58	$1,114.60	$1,114.50