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	$238.28	10.612%	$263.5663	$263.57	$263.55	$263.60
Purchase #2	$182.67	3.233%	$188.5757	$188.58	$188.60	$188.60
Purchase #3	$105.75	11.708%	$118.1312	$118.13	$118.15	$118.10
Purchase #4	$115.42	13.481%	$130.9798	$130.98	$131.00	$131.00
Purchase #5	$127.53	6.817%	$136.2237	$136.22	$136.20	$136.20
Purchase #6	$57.86	6.406%	$61.5665	$61.57	$61.55	$61.60
Purchase #7	$188.45	5.557%	$198.9222	$198.92	$198.90	$198.90
7 purchase totals =	$1,015.96		$1,097.9654	$1,097.97	$1,097.95	$1,098.00