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	$103.61	7.798%	$111.6895	$111.69	$111.70	$111.70
Purchase #2	$185.48	11.723%	$207.2238	$207.22	$207.20	$207.20
Purchase #3	$129.93	12.231%	$145.8217	$145.82	$145.80	$145.80
Purchase #4	$211.61	10.737%	$234.3306	$234.33	$234.35	$234.30
Purchase #5	$20.83	3.365%	$21.5309	$21.53	$21.55	$21.50
Purchase #6	$55.54	13.403%	$62.984	$62.98	$63.00	$63.00
Purchase #7	$61.43	3.429%	$63.5364	$63.54	$63.55	$63.50
7 purchase totals =	$768.43		$847.1169	$847.11	$847.15	$847.00