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	$65.53	4.182%	$68.2705	$68.27	$68.25	$68.30
Purchase #2	$159.79	12.111%	$179.1422	$179.14	$179.15	$179.10
Purchase #3	$119.84	6.599%	$127.7482	$127.75	$127.75	$127.70
Purchase #4	$133.31	5.546%	$140.7034	$140.70	$140.70	$140.70
Purchase #5	$98.60	6.175%	$104.6886	$104.69	$104.70	$104.70
Purchase #6	$100.65	4.142%	$104.8189	$104.82	$104.80	$104.80
Purchase #7	$54.65	9.434%	$59.8057	$59.81	$59.80	$59.80
7 purchase totals =	$732.37		$785.1775	$785.18	$785.15	$785.10