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	$182.43	3.536%	$188.8807	$188.88	$188.90	$188.90
Purchase #2	$221.67	8.542%	$240.6051	$240.61	$240.60	$240.60
Purchase #3	$54.61	13.499%	$61.9818	$61.98	$62.00	$62.00
Purchase #4	$135.56	11.264%	$150.8295	$150.83	$150.85	$150.80
Purchase #5	$131.42	11.320%	$146.2967	$146.30	$146.30	$146.30
Purchase #6	$163.99	13.387%	$185.9433	$185.94	$185.95	$185.90
Purchase #7	$234.68	3.153%	$242.0795	$242.08	$242.10	$242.10
7 purchase totals =	$1,124.36		$1,216.6166	$1,216.62	$1,216.70	$1,216.60