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	$201.62	3.848%	$209.3783	$209.38	$209.40	$209.40
Purchase #2	$162.69	10.369%	$179.5593	$179.56	$179.55	$179.60
Purchase #3	$111.52	13.367%	$126.4269	$126.43	$126.45	$126.40
Purchase #4	$100.77	6.540%	$107.3604	$107.36	$107.35	$107.40
Purchase #5	$193.46	4.206%	$201.5969	$201.60	$201.60	$201.60
Purchase #6	$190.42	3.134%	$196.3878	$196.39	$196.40	$196.40
Purchase #7	$69.89	13.167%	$79.0924	$79.09	$79.10	$79.10
7 purchase totals =	$1,030.37		$1,099.8020	$1,099.81	$1,099.85	$1,099.90