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	$96.41	10.294%	$106.3344	$106.33	$106.35	$106.30
Purchase #2	$232.99	9.514%	$255.1567	$255.16	$255.15	$255.20
Purchase #3	$75.92	8.774%	$82.5812	$82.58	$82.60	$82.60
Purchase #4	$66.96	8.590%	$72.7119	$72.71	$72.70	$72.70
Purchase #5	$10.86	6.444%	$11.5598	$11.56	$11.55	$11.60
Purchase #6	$245.53	13.836%	$279.5015	$279.50	$279.50	$279.50
Purchase #7	$250.40	3.716%	$259.7049	$259.70	$259.70	$259.70
7 purchase totals =	$979.07		$1,067.5504	$1,067.54	$1,067.55	$1,067.60