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	$78.56	13.405%	$89.091	$89.09	$89.10	$89.10
Purchase #2	$213.53	4.152%	$222.3958	$222.40	$222.40	$222.40
Purchase #3	$99.30	10.748%	$109.9728	$109.97	$109.95	$110.00
Purchase #4	$249.46	12.414%	$280.428	$280.43	$280.45	$280.40
Purchase #5	$14.37	6.863%	$15.3562	$15.36	$15.35	$15.40
Purchase #6	$158.49	8.843%	$172.5053	$172.51	$172.50	$172.50
Purchase #7	$108.96	6.472%	$116.0119	$116.01	$116.00	$116.00
7 purchase totals =	$922.67		$1,005.7610	$1,005.77	$1,005.75	$1,005.80