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	$222.94	5.446%	$235.0813	$235.08	$235.10	$235.10
Purchase #2	$162.90	3.658%	$168.8589	$168.86	$168.85	$168.90
Purchase #3	$96.60	4.845%	$101.2803	$101.28	$101.30	$101.30
Purchase #4	$96.41	3.131%	$99.4286	$99.43	$99.45	$99.40
Purchase #5	$13.46	13.547%	$15.2834	$15.28	$15.30	$15.30
Purchase #6	$144.55	12.826%	$163.09	$163.09	$163.10	$163.10
Purchase #7	$234.73	9.210%	$256.3486	$256.35	$256.35	$256.30
7 purchase totals =	$971.59		$1,039.3711	$1,039.37	$1,039.45	$1,039.40