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	$131.64	8.178%	$142.4055	$142.41	$142.40	$142.40
Purchase #2	$118.51	4.109%	$123.3796	$123.38	$123.40	$123.40
Purchase #3	$115.77	13.419%	$131.3052	$131.31	$131.30	$131.30
Purchase #4	$143.27	13.688%	$162.8808	$162.88	$162.90	$162.90
Purchase #5	$216.80	9.401%	$237.1814	$237.18	$237.20	$237.20
Purchase #6	$204.47	12.715%	$230.4684	$230.47	$230.45	$230.50
Purchase #7	$217.36	11.157%	$241.6109	$241.61	$241.60	$241.60
7 purchase totals =	$1,147.82		$1,269.2318	$1,269.24	$1,269.25	$1,269.30