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	$183.69	10.596%	$203.1538	$203.15	$203.15	$203.20
Purchase #2	$49.35	9.431%	$54.0042	$54.00	$54.00	$54.00
Purchase #3	$72.36	8.724%	$78.6727	$78.67	$78.65	$78.70
Purchase #4	$247.70	13.343%	$280.7506	$280.75	$280.75	$280.80
Purchase #5	$245.38	3.520%	$254.0174	$254.02	$254.00	$254.00
Purchase #6	$74.36	9.532%	$81.448	$81.45	$81.45	$81.40
Purchase #7	$182.88	7.637%	$196.8465	$196.85	$196.85	$196.80
7 purchase totals =	$1,055.72		$1,148.8932	$1,148.89	$1,148.85	$1,148.90