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	$105.47	9.170%	$115.1416	$115.14	$115.15	$115.10
Purchase #2	$172.37	11.220%	$191.7099	$191.71	$191.70	$191.70
Purchase #3	$71.37	9.295%	$78.0038	$78.00	$78.00	$78.00
Purchase #4	$156.56	9.299%	$171.1185	$171.12	$171.10	$171.10
Purchase #5	$15.26	13.679%	$17.3474	$17.35	$17.35	$17.30
Purchase #6	$7.77	9.668%	$8.5212	$8.52	$8.50	$8.50
Purchase #7	$91.28	13.678%	$103.7653	$103.77	$103.75	$103.80
7 purchase totals =	$620.08		$685.6077	$685.61	$685.55	$685.50