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	$215.34	4.668%	$225.3921	$225.39	$225.40	$225.40
Purchase #2	$104.53	8.724%	$113.6492	$113.65	$113.65	$113.60
Purchase #3	$112.45	5.824%	$118.9991	$119.00	$119.00	$119.00
Purchase #4	$159.47	12.570%	$179.5154	$179.52	$179.50	$179.50
Purchase #5	$171.50	4.628%	$179.437	$179.44	$179.45	$179.40
Purchase #6	$242.73	9.725%	$266.3355	$266.34	$266.35	$266.30
Purchase #7	$144.96	4.366%	$151.289	$151.29	$151.30	$151.30
7 purchase totals =	$1,150.98		$1,234.6173	$1,234.63	$1,234.65	$1,234.50