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	$91.63	9.539%	$100.3706	$100.37	$100.35	$100.40
Purchase #2	$186.84	5.222%	$196.5968	$196.60	$196.60	$196.60
Purchase #3	$20.33	7.282%	$21.8104	$21.81	$21.80	$21.80
Purchase #4	$201.45	7.151%	$215.8557	$215.86	$215.85	$215.90
Purchase #5	$196.77	3.182%	$203.0312	$203.03	$203.05	$203.00
Purchase #6	$11.68	8.367%	$12.6573	$12.66	$12.65	$12.70
Purchase #7	$248.35	5.857%	$262.8959	$262.90	$262.90	$262.90
7 purchase totals =	$957.05		$1,013.2179	$1,013.23	$1,013.20	$1,013.30