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	$45.49	13.660%	$51.7039	$51.70	$51.70	$51.70
Purchase #2	$126.27	10.505%	$139.5347	$139.53	$139.55	$139.50
Purchase #3	$239.25	6.292%	$254.3036	$254.30	$254.30	$254.30
Purchase #4	$168.27	10.129%	$185.3141	$185.31	$185.30	$185.30
Purchase #5	$11.68	6.137%	$12.3968	$12.40	$12.40	$12.40
Purchase #6	$193.66	8.164%	$209.4704	$209.47	$209.45	$209.50
Purchase #7	$166.69	7.682%	$179.4951	$179.50	$179.50	$179.50
7 purchase totals =	$951.31		$1,032.2186	$1,032.21	$1,032.20	$1,032.20