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	$147.35	7.272%	$158.0653	$158.07	$158.05	$158.10
Purchase #2	$161.55	4.268%	$168.445	$168.45	$168.45	$168.40
Purchase #3	$13.58	9.440%	$14.862	$14.86	$14.85	$14.90
Purchase #4	$34.86	3.270%	$35.9999	$36.00	$36.00	$36.00
Purchase #5	$53.45	13.453%	$60.6406	$60.64	$60.65	$60.60
Purchase #6	$209.78	10.460%	$231.723	$231.72	$231.70	$231.70
Purchase #7	$40.59	8.124%	$43.8875	$43.89	$43.90	$43.90
7 purchase totals =	$661.16		$713.6233	$713.63	$713.60	$713.60