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	$197.75	12.269%	$222.0119	$222.01	$222.00	$222.00
Purchase #2	$8.25	9.561%	$9.0388	$9.04	$9.05	$9.00
Purchase #3	$244.79	13.409%	$277.6139	$277.61	$277.60	$277.60
Purchase #4	$204.38	3.128%	$210.773	$210.77	$210.75	$210.80
Purchase #5	$56.52	5.837%	$59.8191	$59.82	$59.80	$59.80
Purchase #6	$164.96	10.616%	$182.4722	$182.47	$182.45	$182.50
Purchase #7	$166.66	8.668%	$181.1061	$181.11	$181.10	$181.10
7 purchase totals =	$1,043.31		$1,142.8350	$1,142.83	$1,142.75	$1,142.80