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	$156.61	3.675%	$162.3654	$162.37	$162.35	$162.40
Purchase #2	$171.70	9.759%	$188.4562	$188.46	$188.45	$188.50
Purchase #3	$106.74	13.724%	$121.389	$121.39	$121.40	$121.40
Purchase #4	$44.44	3.839%	$46.1461	$46.15	$46.15	$46.10
Purchase #5	$30.50	5.182%	$32.0805	$32.08	$32.10	$32.10
Purchase #6	$117.56	9.208%	$128.3849	$128.38	$128.40	$128.40
Purchase #7	$83.92	6.667%	$89.5149	$89.51	$89.50	$89.50
7 purchase totals =	$711.47		$768.3370	$768.34	$768.35	$768.40