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	$95.61	10.372%	$105.5267	$105.53	$105.55	$105.50
Purchase #2	$161.25	9.466%	$176.5139	$176.51	$176.50	$176.50
Purchase #3	$170.57	8.822%	$185.6177	$185.62	$185.60	$185.60
Purchase #4	$85.43	4.157%	$88.9813	$88.98	$89.00	$89.00
Purchase #5	$222.43	10.716%	$246.2656	$246.27	$246.25	$246.30
Purchase #6	$134.95	12.220%	$151.4409	$151.44	$151.45	$151.40
Purchase #7	$185.58	8.539%	$201.4267	$201.43	$201.45	$201.40
7 purchase totals =	$1,055.82		$1,155.7728	$1,155.78	$1,155.80	$1,155.70