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	$77.62	5.615%	$81.9784	$81.98	$82.00	$82.00
Purchase #2	$68.68	11.190%	$76.3653	$76.37	$76.35	$76.40
Purchase #3	$68.61	13.812%	$78.0864	$78.09	$78.10	$78.10
Purchase #4	$178.86	7.864%	$192.9256	$192.93	$192.95	$192.90
Purchase #5	$78.34	6.382%	$83.3397	$83.34	$83.35	$83.30
Purchase #6	$78.45	5.384%	$82.6737	$82.67	$82.65	$82.70
Purchase #7	$27.77	10.749%	$30.755	$30.76	$30.75	$30.80
7 purchase totals =	$578.33		$626.1241	$626.14	$626.15	$626.20