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	$144.87	9.651%	$158.8514	$158.85	$158.85	$158.90
Purchase #2	$89.66	9.827%	$98.4709	$98.47	$98.45	$98.50
Purchase #3	$194.84	8.517%	$211.4345	$211.43	$211.45	$211.40
Purchase #4	$212.28	13.239%	$240.3837	$240.38	$240.40	$240.40
Purchase #5	$192.96	10.159%	$212.5628	$212.56	$212.55	$212.60
Purchase #6	$198.87	13.276%	$225.272	$225.27	$225.25	$225.30
Purchase #7	$183.50	6.854%	$196.0771	$196.08	$196.10	$196.10
7 purchase totals =	$1,216.98		$1,343.0524	$1,343.04	$1,343.05	$1,343.20