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	$153.95	12.279%	$172.8535	$172.85	$172.85	$172.90
Purchase #2	$248.77	12.720%	$280.4135	$280.41	$280.40	$280.40
Purchase #3	$150.30	3.245%	$155.1772	$155.18	$155.20	$155.20
Purchase #4	$244.81	4.109%	$254.8692	$254.87	$254.85	$254.90
Purchase #5	$199.40	5.492%	$210.351	$210.35	$210.35	$210.40
Purchase #6	$160.42	12.831%	$181.0035	$181.00	$181.00	$181.00
Purchase #7	$99.45	11.689%	$111.0747	$111.07	$111.05	$111.10
7 purchase totals =	$1,257.10		$1,365.7426	$1,365.73	$1,365.70	$1,365.90