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	$19.69	3.531%	$20.3853	$20.39	$20.40	$20.40
Purchase #2	$223.68	6.490%	$238.1968	$238.20	$238.20	$238.20
Purchase #3	$144.59	13.744%	$164.4624	$164.46	$164.45	$164.50
Purchase #4	$208.53	4.347%	$217.5948	$217.59	$217.60	$217.60
Purchase #5	$33.72	4.162%	$35.1234	$35.12	$35.10	$35.10
Purchase #6	$71.32	4.515%	$74.5401	$74.54	$74.55	$74.50
Purchase #7	$56.51	5.632%	$59.6926	$59.69	$59.70	$59.70
7 purchase totals =	$758.04		$809.9954	$809.99	$810.00	$810.00