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	$108.42	8.672%	$117.8222	$117.82	$117.80	$117.80
Purchase #2	$169.25	6.202%	$179.7469	$179.75	$179.75	$179.70
Purchase #3	$74.71	5.497%	$78.8168	$78.82	$78.80	$78.80
Purchase #4	$197.94	12.856%	$223.3872	$223.39	$223.40	$223.40
Purchase #5	$232.92	4.357%	$243.0683	$243.07	$243.05	$243.10
Purchase #6	$37.74	13.549%	$42.8534	$42.85	$42.85	$42.90
Purchase #7	$138.95	6.344%	$147.765	$147.77	$147.75	$147.80
7 purchase totals =	$959.93		$1,033.4598	$1,033.47	$1,033.40	$1,033.50