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	$224.53	11.417%	$250.1646	$250.16	$250.15	$250.20
Purchase #2	$233.42	9.852%	$256.4165	$256.42	$256.40	$256.40
Purchase #3	$159.83	9.572%	$175.1289	$175.13	$175.15	$175.10
Purchase #4	$137.45	10.767%	$152.2492	$152.25	$152.25	$152.20
Purchase #5	$133.52	3.687%	$138.4429	$138.44	$138.45	$138.40
Purchase #6	$127.91	4.872%	$134.1418	$134.14	$134.15	$134.10
Purchase #7	$183.38	13.618%	$208.3527	$208.35	$208.35	$208.40
7 purchase totals =	$1,200.04		$1,314.8966	$1,314.89	$1,314.90	$1,314.80