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	$81.40	4.845%	$85.3438	$85.34	$85.35	$85.30
Purchase #2	$148.84	6.613%	$158.6828	$158.68	$158.70	$158.70
Purchase #3	$88.61	3.620%	$91.8177	$91.82	$91.80	$91.80
Purchase #4	$111.27	7.783%	$119.9301	$119.93	$119.95	$119.90
Purchase #5	$242.48	4.564%	$253.5468	$253.55	$253.55	$253.50
Purchase #6	$153.55	6.536%	$163.586	$163.59	$163.60	$163.60
Purchase #7	$115.88	13.696%	$131.7509	$131.75	$131.75	$131.80
7 purchase totals =	$942.03		$1,004.6581	$1,004.66	$1,004.70	$1,004.60