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	$59.75	13.190%	$67.631	$67.63	$67.65	$67.60
Purchase #2	$61.87	9.621%	$67.8225	$67.82	$67.80	$67.80
Purchase #3	$126.61	10.848%	$140.3447	$140.34	$140.35	$140.30
Purchase #4	$135.62	5.542%	$143.1361	$143.14	$143.15	$143.10
Purchase #5	$28.45	13.617%	$32.324	$32.32	$32.30	$32.30
Purchase #6	$189.45	12.685%	$213.4817	$213.48	$213.50	$213.50
Purchase #7	$128.46	8.855%	$139.8351	$139.84	$139.85	$139.80
7 purchase totals =	$730.21		$804.5751	$804.57	$804.60	$804.40