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	$27.57	4.149%	$28.7139	$28.71	$28.70	$28.70
Purchase #2	$158.71	9.589%	$173.9287	$173.93	$173.95	$173.90
Purchase #3	$79.48	12.604%	$89.4977	$89.50	$89.50	$89.50
Purchase #4	$157.48	13.517%	$178.7666	$178.77	$178.75	$178.80
Purchase #5	$148.59	12.816%	$167.6333	$167.63	$167.65	$167.60
Purchase #6	$107.27	3.579%	$111.1092	$111.11	$111.10	$111.10
Purchase #7	$248.25	12.535%	$279.3681	$279.37	$279.35	$279.40
7 purchase totals =	$927.35		$1,029.0175	$1,029.02	$1,029.00	$1,029.00