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	$122.41	13.793%	$139.294	$139.29	$139.30	$139.30
Purchase #2	$48.97	7.250%	$52.5203	$52.52	$52.50	$52.50
Purchase #3	$80.93	10.760%	$89.6381	$89.64	$89.65	$89.60
Purchase #4	$134.81	5.403%	$142.0938	$142.09	$142.10	$142.10
Purchase #5	$203.37	5.266%	$214.0795	$214.08	$214.10	$214.10
Purchase #6	$223.45	13.501%	$253.618	$253.62	$253.60	$253.60
Purchase #7	$181.74	12.173%	$203.8632	$203.86	$203.85	$203.90
7 purchase totals =	$995.68		$1,095.1069	$1,095.10	$1,095.10	$1,095.10