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	$187.61	9.609%	$205.6374	$205.64	$205.65	$205.60
Purchase #2	$219.28	7.570%	$235.8795	$235.88	$235.90	$235.90
Purchase #3	$98.81	13.768%	$112.4142	$112.41	$112.40	$112.40
Purchase #4	$133.93	7.677%	$144.2118	$144.21	$144.20	$144.20
Purchase #5	$112.71	12.713%	$127.0388	$127.04	$127.05	$127.00
Purchase #6	$131.47	7.397%	$141.1948	$141.19	$141.20	$141.20
Purchase #7	$156.76	9.237%	$171.2399	$171.24	$171.25	$171.20
7 purchase totals =	$1,040.57		$1,137.6164	$1,137.61	$1,137.65	$1,137.50