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	$142.86	10.556%	$157.9403	$157.94	$157.95	$157.90
Purchase #2	$102.46	11.704%	$114.4519	$114.45	$114.45	$114.50
Purchase #3	$89.50	13.496%	$101.5789	$101.58	$101.60	$101.60
Purchase #4	$210.69	3.740%	$218.5698	$218.57	$218.55	$218.60
Purchase #5	$218.81	4.561%	$228.7899	$228.79	$228.80	$228.80
Purchase #6	$64.78	11.286%	$72.0911	$72.09	$72.10	$72.10
Purchase #7	$216.80	5.838%	$229.4568	$229.46	$229.45	$229.50
7 purchase totals =	$1,045.90		$1,122.8787	$1,122.88	$1,122.90	$1,123.00