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	$202.77	3.635%	$210.1407	$210.14	$210.15	$210.10
Purchase #2	$37.97	3.151%	$39.1664	$39.17	$39.15	$39.20
Purchase #3	$80.73	12.296%	$90.6566	$90.66	$90.65	$90.70
Purchase #4	$40.64	4.346%	$42.4062	$42.41	$42.40	$42.40
Purchase #5	$96.64	13.430%	$109.6188	$109.62	$109.60	$109.60
Purchase #6	$217.66	5.121%	$228.8064	$228.81	$228.80	$228.80
Purchase #7	$40.68	7.792%	$43.8498	$43.85	$43.85	$43.80
7 purchase totals =	$717.09		$764.6449	$764.66	$764.60	$764.60