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	$234.49	10.373%	$258.8136	$258.81	$258.80	$258.80
Purchase #2	$16.46	12.280%	$18.4813	$18.48	$18.50	$18.50
Purchase #3	$123.58	9.654%	$135.5104	$135.51	$135.50	$135.50
Purchase #4	$230.39	3.614%	$238.7163	$238.72	$238.70	$238.70
Purchase #5	$22.80	7.448%	$24.4981	$24.50	$24.50	$24.50
Purchase #6	$190.31	13.675%	$216.3349	$216.33	$216.35	$216.30
Purchase #7	$164.53	4.719%	$172.2942	$172.29	$172.30	$172.30
7 purchase totals =	$982.56		$1,064.6488	$1,064.64	$1,064.65	$1,064.60