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	$216.72	10.764%	$240.0477	$240.05	$240.05	$240.00
Purchase #2	$215.72	11.612%	$240.7694	$240.77	$240.75	$240.80
Purchase #3	$239.93	7.686%	$258.371	$258.37	$258.35	$258.40
Purchase #4	$177.33	9.615%	$194.3803	$194.38	$194.40	$194.40
Purchase #5	$246.41	13.349%	$279.3033	$279.30	$279.30	$279.30
Purchase #6	$123.31	6.452%	$131.266	$131.27	$131.25	$131.30
Purchase #7	$62.94	5.603%	$66.4665	$66.47	$66.45	$66.50
7 purchase totals =	$1,282.36		$1,410.6042	$1,410.61	$1,410.55	$1,410.70