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	$169.65	12.132%	$190.2319	$190.23	$190.25	$190.20
Purchase #2	$41.49	4.537%	$43.3724	$43.37	$43.35	$43.40
Purchase #3	$229.49	9.721%	$251.7987	$251.80	$251.80	$251.80
Purchase #4	$207.34	3.681%	$214.9722	$214.97	$214.95	$215.00
Purchase #5	$128.83	6.690%	$137.4487	$137.45	$137.45	$137.40
Purchase #6	$127.37	8.215%	$137.8334	$137.83	$137.85	$137.80
Purchase #7	$151.96	3.221%	$156.8546	$156.85	$156.85	$156.90
7 purchase totals =	$1,056.13		$1,132.5119	$1,132.50	$1,132.50	$1,132.50