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	$163.43	9.787%	$179.4249	$179.42	$179.40	$179.40
Purchase #2	$225.47	7.194%	$241.6903	$241.69	$241.70	$241.70
Purchase #3	$55.39	12.683%	$62.4151	$62.42	$62.40	$62.40
Purchase #4	$165.46	4.348%	$172.6542	$172.65	$172.65	$172.70
Purchase #5	$169.56	4.578%	$177.3225	$177.32	$177.30	$177.30
Purchase #6	$13.69	8.486%	$14.8517	$14.85	$14.85	$14.90
Purchase #7	$184.27	3.581%	$190.8687	$190.87	$190.85	$190.90
7 purchase totals =	$977.27		$1,039.2274	$1,039.22	$1,039.15	$1,039.30