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	$157.85	10.416%	$174.2917	$174.29	$174.30	$174.30
Purchase #2	$151.30	10.269%	$166.837	$166.84	$166.85	$166.80
Purchase #3	$38.81	9.721%	$42.5827	$42.58	$42.60	$42.60
Purchase #4	$73.80	4.866%	$77.3911	$77.39	$77.40	$77.40
Purchase #5	$153.97	9.339%	$168.3493	$168.35	$168.35	$168.30
Purchase #6	$130.39	7.152%	$139.7155	$139.72	$139.70	$139.70
Purchase #7	$146.35	12.438%	$164.553	$164.55	$164.55	$164.60
7 purchase totals =	$852.47		$933.7203	$933.72	$933.75	$933.70