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	$56.40	7.191%	$60.4557	$60.46	$60.45	$60.50
Purchase #2	$169.51	11.149%	$188.4087	$188.41	$188.40	$188.40
Purchase #3	$185.78	4.651%	$194.4206	$194.42	$194.40	$194.40
Purchase #4	$61.65	13.141%	$69.7514	$69.75	$69.75	$69.80
Purchase #5	$66.72	7.584%	$71.78	$71.78	$71.80	$71.80
Purchase #6	$133.69	12.249%	$150.0657	$150.07	$150.05	$150.10
Purchase #7	$47.40	9.220%	$51.7703	$51.77	$51.75	$51.80
7 purchase totals =	$721.15		$786.6524	$786.66	$786.60	$786.80