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	$213.31	8.359%	$231.1406	$231.14	$231.15	$231.10
Purchase #2	$202.43	13.140%	$229.0293	$229.03	$229.05	$229.00
Purchase #3	$41.66	4.162%	$43.3939	$43.39	$43.40	$43.40
Purchase #4	$50.65	10.723%	$56.0812	$56.08	$56.10	$56.10
Purchase #5	$170.40	8.834%	$185.4531	$185.45	$185.45	$185.50
Purchase #6	$217.87	9.167%	$237.8421	$237.84	$237.85	$237.80
Purchase #7	$199.89	13.752%	$227.3789	$227.38	$227.40	$227.40
7 purchase totals =	$1,096.21		$1,210.3191	$1,210.31	$1,210.40	$1,210.30