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	$59.90	7.522%	$64.4057	$64.41	$64.40	$64.40
Purchase #2	$148.93	13.786%	$169.4615	$169.46	$169.45	$169.50
Purchase #3	$95.50	5.106%	$100.3762	$100.38	$100.40	$100.40
Purchase #4	$9.85	10.742%	$10.9081	$10.91	$10.90	$10.90
Purchase #5	$203.32	12.516%	$228.7675	$228.77	$228.75	$228.80
Purchase #6	$51.83	4.344%	$54.0815	$54.08	$54.10	$54.10
Purchase #7	$63.77	12.135%	$71.5085	$71.51	$71.50	$71.50
7 purchase totals =	$633.10		$699.5090	$699.52	$699.50	$699.60