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	$64.84	11.797%	$72.4892	$72.49	$72.50	$72.50
Purchase #2	$171.36	8.187%	$185.3892	$185.39	$185.40	$185.40
Purchase #3	$47.70	8.738%	$51.868	$51.87	$51.85	$51.90
Purchase #4	$66.31	10.667%	$73.3833	$73.38	$73.40	$73.40
Purchase #5	$60.35	5.440%	$63.633	$63.63	$63.65	$63.60
Purchase #6	$38.42	13.860%	$43.745	$43.75	$43.75	$43.70
Purchase #7	$241.53	11.733%	$269.8687	$269.87	$269.85	$269.90
7 purchase totals =	$690.51		$760.3764	$760.38	$760.40	$760.40