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	$220.91	6.118%	$234.4253	$234.43	$234.45	$234.40
Purchase #2	$84.91	5.731%	$89.7762	$89.78	$89.80	$89.80
Purchase #3	$20.29	11.584%	$22.6404	$22.64	$22.65	$22.60
Purchase #4	$138.27	5.134%	$145.3688	$145.37	$145.35	$145.40
Purchase #5	$238.47	9.640%	$261.4585	$261.46	$261.45	$261.50
Purchase #6	$59.70	8.103%	$64.5375	$64.54	$64.55	$64.50
Purchase #7	$142.51	5.520%	$150.3766	$150.38	$150.40	$150.40
7 purchase totals =	$905.06		$968.5833	$968.60	$968.65	$968.60