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	$55.44	10.197%	$61.0932	$61.09	$61.10	$61.10
Purchase #2	$179.31	3.328%	$185.2774	$185.28	$185.30	$185.30
Purchase #3	$32.62	5.811%	$34.5155	$34.52	$34.50	$34.50
Purchase #4	$102.26	13.697%	$116.2666	$116.27	$116.25	$116.30
Purchase #5	$136.81	3.569%	$141.6927	$141.69	$141.70	$141.70
Purchase #6	$108.65	13.684%	$123.5177	$123.52	$123.50	$123.50
Purchase #7	$82.99	4.175%	$86.4548	$86.45	$86.45	$86.50
7 purchase totals =	$698.08		$748.8179	$748.82	$748.80	$748.90