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	$189.50	8.754%	$206.0888	$206.09	$206.10	$206.10
Purchase #2	$157.48	6.215%	$167.2674	$167.27	$167.25	$167.30
Purchase #3	$20.28	6.481%	$21.5943	$21.59	$21.60	$21.60
Purchase #4	$225.54	8.353%	$244.3794	$244.38	$244.40	$244.40
Purchase #5	$59.54	4.470%	$62.2014	$62.20	$62.20	$62.20
Purchase #6	$172.60	13.812%	$196.4395	$196.44	$196.45	$196.40
Purchase #7	$54.41	12.829%	$61.3903	$61.39	$61.40	$61.40
7 purchase totals =	$879.35		$959.3611	$959.36	$959.40	$959.40