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	$227.66	7.846%	$245.5222	$245.52	$245.50	$245.50
Purchase #2	$36.31	4.455%	$37.9276	$37.93	$37.95	$37.90
Purchase #3	$19.71	10.664%	$21.8119	$21.81	$21.80	$21.80
Purchase #4	$66.56	8.731%	$72.3714	$72.37	$72.35	$72.40
Purchase #5	$62.35	4.487%	$65.1476	$65.15	$65.15	$65.10
Purchase #6	$148.64	3.736%	$154.1932	$154.19	$154.20	$154.20
Purchase #7	$221.78	4.125%	$230.9284	$230.93	$230.95	$230.90
7 purchase totals =	$783.01		$827.9023	$827.90	$827.90	$827.80