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	$76.78	12.595%	$86.4504	$86.45	$86.45	$86.50
Purchase #2	$217.48	12.520%	$244.7085	$244.71	$244.70	$244.70
Purchase #3	$28.75	12.867%	$32.4493	$32.45	$32.45	$32.40
Purchase #4	$90.34	3.362%	$93.3772	$93.38	$93.40	$93.40
Purchase #5	$57.78	9.803%	$63.4442	$63.44	$63.45	$63.40
Purchase #6	$172.86	9.685%	$189.6015	$189.60	$189.60	$189.60
Purchase #7	$49.62	13.854%	$56.4944	$56.49	$56.50	$56.50
7 purchase totals =	$693.61		$766.5255	$766.52	$766.55	$766.50