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	$210.59	11.548%	$234.9089	$234.91	$234.90	$234.90
Purchase #2	$173.30	13.240%	$196.2449	$196.24	$196.25	$196.20
Purchase #3	$36.99	9.643%	$40.5569	$40.56	$40.55	$40.60
Purchase #4	$156.88	10.772%	$173.7791	$173.78	$173.80	$173.80
Purchase #5	$226.45	6.624%	$241.45	$241.45	$241.45	$241.50
Purchase #6	$247.39	13.420%	$280.5897	$280.59	$280.60	$280.60
Purchase #7	$82.70	8.765%	$89.9487	$89.95	$89.95	$89.90
7 purchase totals =	$1,134.30		$1,257.4782	$1,257.48	$1,257.50	$1,257.50