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	$95.67	9.184%	$104.4563	$104.46	$104.45	$104.50
Purchase #2	$11.81	3.853%	$12.265	$12.27	$12.25	$12.30
Purchase #3	$208.52	10.830%	$231.1027	$231.10	$231.10	$231.10
Purchase #4	$49.55	10.287%	$54.6472	$54.65	$54.65	$54.60
Purchase #5	$198.50	12.498%	$223.3085	$223.31	$223.30	$223.30
Purchase #6	$141.95	11.692%	$158.5468	$158.55	$158.55	$158.50
Purchase #7	$61.42	6.776%	$65.5818	$65.58	$65.60	$65.60
7 purchase totals =	$767.42		$849.9083	$849.92	$849.90	$849.90