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	$161.54	11.779%	$180.5678	$180.57	$180.55	$180.60
Purchase #2	$199.35	9.550%	$218.3879	$218.39	$218.40	$218.40
Purchase #3	$102.30	11.671%	$114.2394	$114.24	$114.25	$114.20
Purchase #4	$244.71	6.259%	$260.0264	$260.03	$260.05	$260.00
Purchase #5	$127.85	4.395%	$133.469	$133.47	$133.45	$133.50
Purchase #6	$115.25	13.362%	$130.6497	$130.65	$130.65	$130.60
Purchase #7	$53.66	10.852%	$59.4832	$59.48	$59.50	$59.50
7 purchase totals =	$1,004.66		$1,096.8234	$1,096.83	$1,096.85	$1,096.80