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	$149.63	9.837%	$164.3491	$164.35	$164.35	$164.30
Purchase #2	$185.75	9.534%	$203.4594	$203.46	$203.45	$203.50
Purchase #3	$198.96	3.435%	$205.7943	$205.79	$205.80	$205.80
Purchase #4	$213.45	4.553%	$223.1684	$223.17	$223.15	$223.20
Purchase #5	$95.80	4.326%	$99.9443	$99.94	$99.95	$99.90
Purchase #6	$77.45	6.782%	$82.7027	$82.70	$82.70	$82.70
Purchase #7	$10.85	6.650%	$11.5715	$11.57	$11.55	$11.60
7 purchase totals =	$931.89		$990.9897	$990.98	$990.95	$991.00