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	$129.71	12.349%	$145.7279	$145.73	$145.75	$145.70
Purchase #2	$188.37	13.389%	$213.5909	$213.59	$213.60	$213.60
Purchase #3	$34.85	10.222%	$38.4124	$38.41	$38.40	$38.40
Purchase #4	$184.54	11.332%	$205.4521	$205.45	$205.45	$205.50
Purchase #5	$21.89	12.407%	$24.6059	$24.61	$24.60	$24.60
Purchase #6	$155.79	8.223%	$168.6006	$168.60	$168.60	$168.60
Purchase #7	$249.92	12.205%	$280.4227	$280.42	$280.40	$280.40
7 purchase totals =	$965.07		$1,076.8125	$1,076.81	$1,076.80	$1,076.80