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	$153.51	12.620%	$172.883	$172.88	$172.90	$172.90
Purchase #2	$9.48	12.373%	$10.653	$10.65	$10.65	$10.70
Purchase #3	$73.91	11.511%	$82.4178	$82.42	$82.40	$82.40
Purchase #4	$128.52	13.135%	$145.4011	$145.40	$145.40	$145.40
Purchase #5	$105.83	9.488%	$115.8712	$115.87	$115.85	$115.90
Purchase #6	$241.56	5.550%	$254.9666	$254.97	$254.95	$255.00
Purchase #7	$62.45	8.525%	$67.7739	$67.77	$67.75	$67.80
7 purchase totals =	$775.26		$849.9666	$849.96	$849.90	$850.10