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	$237.31	10.814%	$262.9727	$262.97	$262.95	$263.00
Purchase #2	$118.87	10.521%	$131.3763	$131.38	$131.40	$131.40
Purchase #3	$42.42	6.592%	$45.2163	$45.22	$45.20	$45.20
Purchase #4	$184.32	3.384%	$190.5574	$190.56	$190.55	$190.60
Purchase #5	$185.35	8.858%	$201.7683	$201.77	$201.75	$201.80
Purchase #6	$39.35	8.342%	$42.6326	$42.63	$42.65	$42.60
Purchase #7	$155.35	6.508%	$165.4602	$165.46	$165.45	$165.50
7 purchase totals =	$962.97		$1,039.9838	$1,039.99	$1,039.95	$1,040.10