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	$134.31	10.817%	$148.8383	$148.84	$148.85	$148.80
Purchase #2	$89.46	11.691%	$99.9188	$99.92	$99.90	$99.90
Purchase #3	$182.75	4.343%	$190.6868	$190.69	$190.70	$190.70
Purchase #4	$247.56	3.371%	$255.9052	$255.91	$255.90	$255.90
Purchase #5	$103.41	13.330%	$117.1946	$117.19	$117.20	$117.20
Purchase #6	$112.64	3.157%	$116.196	$116.20	$116.20	$116.20
Purchase #7	$115.37	4.536%	$120.6032	$120.60	$120.60	$120.60
7 purchase totals =	$985.50		$1,049.3429	$1,049.35	$1,049.35	$1,049.30