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	$112.35	9.530%	$123.057	$123.06	$123.05	$123.10
Purchase #2	$160.81	3.661%	$166.6973	$166.70	$166.70	$166.70
Purchase #3	$77.72	5.527%	$82.0156	$82.02	$82.00	$82.00
Purchase #4	$77.67	3.369%	$80.2867	$80.29	$80.30	$80.30
Purchase #5	$148.85	11.655%	$166.1985	$166.20	$166.20	$166.20
Purchase #6	$158.37	8.253%	$171.4403	$171.44	$171.45	$171.40
Purchase #7	$187.92	6.492%	$200.1198	$200.12	$200.10	$200.10
7 purchase totals =	$923.69		$989.8152	$989.83	$989.80	$989.80