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	$235.96	11.242%	$262.4866	$262.49	$262.50	$262.50
Purchase #2	$87.88	3.153%	$90.6509	$90.65	$90.65	$90.70
Purchase #3	$6.72	8.146%	$7.2674	$7.27	$7.25	$7.30
Purchase #4	$42.53	11.771%	$47.5362	$47.54	$47.55	$47.50
Purchase #5	$134.31	9.853%	$147.5436	$147.54	$147.55	$147.50
Purchase #6	$181.41	8.254%	$196.3836	$196.38	$196.40	$196.40
Purchase #7	$48.36	3.578%	$50.0903	$50.09	$50.10	$50.10
7 purchase totals =	$737.17		$801.9586	$801.96	$802.00	$802.00