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	$175.98	4.456%	$183.8217	$183.82	$183.80	$183.80
Purchase #2	$180.35	12.643%	$203.1517	$203.15	$203.15	$203.20
Purchase #3	$82.70	7.784%	$89.1374	$89.14	$89.15	$89.10
Purchase #4	$242.55	12.184%	$272.1023	$272.10	$272.10	$272.10
Purchase #5	$90.25	5.391%	$95.1154	$95.12	$95.10	$95.10
Purchase #6	$142.71	11.324%	$158.8705	$158.87	$158.85	$158.90
Purchase #7	$45.47	4.126%	$47.3461	$47.35	$47.35	$47.30
7 purchase totals =	$960.01		$1,049.5451	$1,049.55	$1,049.50	$1,049.50