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	$14.70	10.671%	$16.2686	$16.27	$16.25	$16.30
Purchase #2	$176.63	11.330%	$196.6422	$196.64	$196.65	$196.60
Purchase #3	$144.93	6.515%	$154.3722	$154.37	$154.35	$154.40
Purchase #4	$135.59	9.262%	$148.1483	$148.15	$148.15	$148.10
Purchase #5	$73.81	6.297%	$78.4578	$78.46	$78.45	$78.50
Purchase #6	$245.33	6.844%	$262.1204	$262.12	$262.10	$262.10
Purchase #7	$198.73	3.298%	$205.2841	$205.28	$205.30	$205.30
7 purchase totals =	$989.72		$1,061.2936	$1,061.29	$1,061.25	$1,061.30