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	$105.46	4.736%	$110.4546	$110.45	$110.45	$110.50
Purchase #2	$74.61	4.763%	$78.1637	$78.16	$78.15	$78.20
Purchase #3	$51.49	5.771%	$54.4615	$54.46	$54.45	$54.50
Purchase #4	$138.73	8.870%	$151.0354	$151.04	$151.05	$151.00
Purchase #5	$130.92	3.734%	$135.8086	$135.81	$135.80	$135.80
Purchase #6	$92.61	10.771%	$102.585	$102.59	$102.60	$102.60
Purchase #7	$172.78	5.206%	$181.7749	$181.77	$181.75	$181.80
7 purchase totals =	$766.60		$814.2837	$814.28	$814.25	$814.40