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	$103.47	4.828%	$108.4655	$108.47	$108.45	$108.50
Purchase #2	$109.51	3.663%	$113.5214	$113.52	$113.50	$113.50
Purchase #3	$122.64	3.693%	$127.1691	$127.17	$127.15	$127.20
Purchase #4	$39.60	9.400%	$43.3224	$43.32	$43.30	$43.30
Purchase #5	$38.95	3.771%	$40.4188	$40.42	$40.40	$40.40
Purchase #6	$179.54	10.463%	$198.3253	$198.33	$198.35	$198.30
Purchase #7	$77.75	8.632%	$84.4614	$84.46	$84.45	$84.50
7 purchase totals =	$671.46		$715.6839	$715.69	$715.60	$715.70