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	$133.26	10.351%	$147.0537	$147.05	$147.05	$147.10
Purchase #2	$118.96	8.113%	$128.6112	$128.61	$128.60	$128.60
Purchase #3	$231.94	9.489%	$253.9488	$253.95	$253.95	$253.90
Purchase #4	$70.42	11.399%	$78.4472	$78.45	$78.45	$78.40
Purchase #5	$72.89	7.650%	$78.4661	$78.47	$78.45	$78.50
Purchase #6	$17.83	11.546%	$19.8887	$19.89	$19.90	$19.90
Purchase #7	$186.84	3.642%	$193.6447	$193.64	$193.65	$193.60
7 purchase totals =	$832.14		$900.0604	$900.06	$900.05	$900.00