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	$226.83	6.693%	$242.0117	$242.01	$242.00	$242.00
Purchase #2	$200.39	13.210%	$226.8615	$226.86	$226.85	$226.90
Purchase #3	$178.28	4.588%	$186.4595	$186.46	$186.45	$186.50
Purchase #4	$97.83	8.287%	$105.9372	$105.94	$105.95	$105.90
Purchase #5	$63.72	11.177%	$70.842	$70.84	$70.85	$70.80
Purchase #6	$222.71	13.304%	$252.3393	$252.34	$252.35	$252.30
Purchase #7	$186.30	7.501%	$200.2744	$200.27	$200.25	$200.30
7 purchase totals =	$1,176.06		$1,284.7256	$1,284.72	$1,284.70	$1,284.70