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	$98.51	6.615%	$105.0264	$105.03	$105.05	$105.00
Purchase #2	$211.97	5.760%	$224.1795	$224.18	$224.20	$224.20
Purchase #3	$11.51	9.665%	$12.6224	$12.62	$12.60	$12.60
Purchase #4	$246.57	13.651%	$280.2293	$280.23	$280.25	$280.20
Purchase #5	$151.93	11.204%	$168.9522	$168.95	$168.95	$169.00
Purchase #6	$199.73	10.713%	$221.1271	$221.13	$221.15	$221.10
Purchase #7	$54.83	13.597%	$62.2852	$62.29	$62.30	$62.30
7 purchase totals =	$975.05		$1,074.4221	$1,074.43	$1,074.50	$1,074.40