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	$59.83	9.124%	$65.2889	$65.29	$65.30	$65.30
Purchase #2	$244.61	4.366%	$255.2897	$255.29	$255.30	$255.30
Purchase #3	$171.56	9.486%	$187.8342	$187.83	$187.85	$187.80
Purchase #4	$231.71	13.515%	$263.0256	$263.03	$263.05	$263.00
Purchase #5	$45.57	8.447%	$49.4193	$49.42	$49.40	$49.40
Purchase #6	$208.89	7.140%	$223.8047	$223.80	$223.80	$223.80
Purchase #7	$12.71	7.454%	$13.6574	$13.66	$13.65	$13.70
7 purchase totals =	$974.88		$1,058.3198	$1,058.32	$1,058.35	$1,058.30