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	$53.47	11.542%	$59.6415	$59.64	$59.65	$59.60
Purchase #2	$172.39	11.856%	$192.8286	$192.83	$192.85	$192.80
Purchase #3	$225.43	5.581%	$238.0112	$238.01	$238.00	$238.00
Purchase #4	$87.98	13.130%	$99.5318	$99.53	$99.55	$99.50
Purchase #5	$109.37	6.356%	$116.3216	$116.32	$116.30	$116.30
Purchase #6	$5.91	3.569%	$6.1209	$6.12	$6.10	$6.10
Purchase #7	$236.45	7.686%	$254.6235	$254.62	$254.60	$254.60
7 purchase totals =	$891.00		$967.0791	$967.07	$967.05	$966.90