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	$238.31	5.243%	$250.8046	$250.80	$250.80	$250.80
Purchase #2	$40.86	5.239%	$43.0007	$43.00	$43.00	$43.00
Purchase #3	$117.31	9.447%	$128.3923	$128.39	$128.40	$128.40
Purchase #4	$179.38	9.298%	$196.0588	$196.06	$196.05	$196.10
Purchase #5	$78.94	7.721%	$85.035	$85.04	$85.05	$85.00
Purchase #6	$15.60	4.640%	$16.3238	$16.32	$16.30	$16.30
Purchase #7	$220.69	11.208%	$245.4249	$245.42	$245.40	$245.40
7 purchase totals =	$891.09		$965.0401	$965.03	$965.00	$965.00