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	$45.88	8.119%	$49.605	$49.61	$49.60	$49.60
Purchase #2	$88.35	9.256%	$96.5277	$96.53	$96.55	$96.50
Purchase #3	$218.61	9.561%	$239.5113	$239.51	$239.50	$239.50
Purchase #4	$241.34	6.386%	$256.752	$256.75	$256.75	$256.80
Purchase #5	$222.36	7.319%	$238.6345	$238.63	$238.65	$238.60
Purchase #6	$161.99	10.788%	$179.4655	$179.47	$179.45	$179.50
Purchase #7	$108.79	10.190%	$119.8757	$119.88	$119.90	$119.90
7 purchase totals =	$1,087.32		$1,180.3717	$1,180.38	$1,180.40	$1,180.40