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	$227.53	12.627%	$256.2602	$256.26	$256.25	$256.30
Purchase #2	$33.54	13.485%	$38.0629	$38.06	$38.05	$38.10
Purchase #3	$138.41	5.409%	$145.8966	$145.90	$145.90	$145.90
Purchase #4	$217.27	13.399%	$246.382	$246.38	$246.40	$246.40
Purchase #5	$148.46	10.825%	$164.5308	$164.53	$164.55	$164.50
Purchase #6	$140.51	10.683%	$155.5207	$155.52	$155.50	$155.50
Purchase #7	$53.26	7.388%	$57.1948	$57.19	$57.20	$57.20
7 purchase totals =	$958.98		$1,063.8480	$1,063.84	$1,063.85	$1,063.90