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	$248.88	12.659%	$280.3857	$280.39	$280.40	$280.40
Purchase #2	$63.61	11.152%	$70.7038	$70.70	$70.70	$70.70
Purchase #3	$149.55	4.515%	$156.3022	$156.30	$156.30	$156.30
Purchase #4	$101.69	10.764%	$112.6359	$112.64	$112.65	$112.60
Purchase #5	$39.29	4.412%	$41.0235	$41.02	$41.00	$41.00
Purchase #6	$204.51	13.182%	$231.4685	$231.47	$231.45	$231.50
Purchase #7	$159.94	5.576%	$168.8583	$168.86	$168.85	$168.90
7 purchase totals =	$967.47		$1,061.3779	$1,061.38	$1,061.35	$1,061.40