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	$95.63	9.696%	$104.9023	$104.90	$104.90	$104.90
Purchase #2	$154.84	3.413%	$160.1247	$160.12	$160.10	$160.10
Purchase #3	$133.43	5.833%	$141.213	$141.21	$141.20	$141.20
Purchase #4	$226.77	12.765%	$255.7172	$255.72	$255.70	$255.70
Purchase #5	$38.30	11.225%	$42.5992	$42.60	$42.60	$42.60
Purchase #6	$145.52	11.107%	$161.6829	$161.68	$161.70	$161.70
Purchase #7	$123.98	10.691%	$137.2347	$137.23	$137.25	$137.20
7 purchase totals =	$918.47		$1,003.4740	$1,003.46	$1,003.45	$1,003.40