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	$207.32	12.862%	$233.9855	$233.99	$234.00	$234.00
Purchase #2	$156.42	5.591%	$165.1654	$165.17	$165.15	$165.20
Purchase #3	$147.57	11.171%	$164.055	$164.06	$164.05	$164.10
Purchase #4	$229.25	13.767%	$260.8108	$260.81	$260.80	$260.80
Purchase #5	$122.87	3.867%	$127.6214	$127.62	$127.60	$127.60
Purchase #6	$156.86	7.493%	$168.6135	$168.61	$168.60	$168.60
Purchase #7	$99.93	9.327%	$109.2505	$109.25	$109.25	$109.30
7 purchase totals =	$1,120.22		$1,229.5021	$1,229.51	$1,229.45	$1,229.60