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	$44.96	10.656%	$49.7509	$49.75	$49.75	$49.80
Purchase #2	$110.83	5.481%	$116.9046	$116.90	$116.90	$116.90
Purchase #3	$241.91	5.753%	$255.8271	$255.83	$255.85	$255.80
Purchase #4	$145.80	10.215%	$160.6935	$160.69	$160.70	$160.70
Purchase #5	$172.47	9.559%	$188.9564	$188.96	$188.95	$189.00
Purchase #6	$63.90	13.197%	$72.3329	$72.33	$72.35	$72.30
Purchase #7	$127.41	11.491%	$142.0507	$142.05	$142.05	$142.10
7 purchase totals =	$907.28		$986.5161	$986.51	$986.55	$986.60