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	$127.93	5.111%	$134.4685	$134.47	$134.45	$134.50
Purchase #2	$233.59	4.291%	$243.6133	$243.61	$243.60	$243.60
Purchase #3	$51.41	7.379%	$55.2035	$55.20	$55.20	$55.20
Purchase #4	$14.70	10.571%	$16.2539	$16.25	$16.25	$16.30
Purchase #5	$147.35	11.416%	$164.1715	$164.17	$164.15	$164.20
Purchase #6	$15.36	11.336%	$17.1012	$17.10	$17.10	$17.10
Purchase #7	$123.86	3.160%	$127.774	$127.77	$127.75	$127.80
7 purchase totals =	$714.20		$758.5859	$758.57	$758.50	$758.70