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	$168.61	9.734%	$185.0225	$185.02	$185.00	$185.00
Purchase #2	$128.45	10.322%	$141.7086	$141.71	$141.70	$141.70
Purchase #3	$177.93	10.457%	$196.5361	$196.54	$196.55	$196.50
Purchase #4	$185.62	10.445%	$205.008	$205.01	$205.00	$205.00
Purchase #5	$82.35	11.208%	$91.5798	$91.58	$91.60	$91.60
Purchase #6	$37.40	7.133%	$40.0677	$40.07	$40.05	$40.10
Purchase #7	$227.86	12.447%	$256.2217	$256.22	$256.20	$256.20
7 purchase totals =	$1,008.22		$1,116.1444	$1,116.15	$1,116.10	$1,116.10