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	$161.61	5.607%	$170.6715	$170.67	$170.65	$170.70
Purchase #2	$214.51	4.357%	$223.8562	$223.86	$223.85	$223.90
Purchase #3	$197.93	9.775%	$217.2777	$217.28	$217.30	$217.30
Purchase #4	$19.27	10.494%	$21.2922	$21.29	$21.30	$21.30
Purchase #5	$63.88	13.328%	$72.3939	$72.39	$72.40	$72.40
Purchase #6	$147.75	7.471%	$158.7884	$158.79	$158.80	$158.80
Purchase #7	$136.62	6.164%	$145.0413	$145.04	$145.05	$145.00
7 purchase totals =	$941.57		$1,009.3212	$1,009.32	$1,009.35	$1,009.40