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	$237.92	5.488%	$250.977	$250.98	$251.00	$251.00
Purchase #2	$59.57	6.826%	$63.6362	$63.64	$63.65	$63.60
Purchase #3	$237.82	10.301%	$262.3178	$262.32	$262.30	$262.30
Purchase #4	$235.91	8.123%	$255.073	$255.07	$255.05	$255.10
Purchase #5	$35.49	8.816%	$38.6188	$38.62	$38.60	$38.60
Purchase #6	$54.37	5.121%	$57.1543	$57.15	$57.15	$57.20
Purchase #7	$83.57	8.649%	$90.798	$90.80	$90.80	$90.80
7 purchase totals =	$944.65		$1,018.5751	$1,018.58	$1,018.55	$1,018.60