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	$205.30	13.674%	$233.3727	$233.37	$233.35	$233.40
Purchase #2	$213.79	5.635%	$225.8371	$225.84	$225.85	$225.80
Purchase #3	$206.89	3.215%	$213.5415	$213.54	$213.55	$213.50
Purchase #4	$89.42	12.242%	$100.3668	$100.37	$100.35	$100.40
Purchase #5	$57.35	4.158%	$59.7346	$59.73	$59.75	$59.70
Purchase #6	$125.68	11.733%	$140.426	$140.43	$140.45	$140.40
Purchase #7	$128.35	13.549%	$145.7401	$145.74	$145.75	$145.70
7 purchase totals =	$1,026.78		$1,119.0188	$1,119.02	$1,119.05	$1,118.90