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	$157.52	10.118%	$173.4579	$173.46	$173.45	$173.50
Purchase #2	$224.33	3.619%	$232.4485	$232.45	$232.45	$232.40
Purchase #3	$104.98	13.849%	$119.5187	$119.52	$119.50	$119.50
Purchase #4	$29.67	6.615%	$31.6327	$31.63	$31.65	$31.60
Purchase #5	$118.82	3.753%	$123.2793	$123.28	$123.30	$123.30
Purchase #6	$237.88	3.779%	$246.8695	$246.87	$246.85	$246.90
Purchase #7	$105.43	5.152%	$110.8618	$110.86	$110.85	$110.90
7 purchase totals =	$978.63		$1,038.0684	$1,038.07	$1,038.05	$1,038.10