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	$154.87	9.505%	$169.5904	$169.59	$169.60	$169.60
Purchase #2	$232.47	4.536%	$243.0148	$243.01	$243.00	$243.00
Purchase #3	$45.86	9.341%	$50.1438	$50.14	$50.15	$50.10
Purchase #4	$158.98	8.298%	$172.1722	$172.17	$172.15	$172.20
Purchase #5	$174.59	8.240%	$188.9762	$188.98	$189.00	$189.00
Purchase #6	$116.70	9.277%	$127.5263	$127.53	$127.55	$127.50
Purchase #7	$51.36	5.158%	$54.0091	$54.01	$54.00	$54.00
7 purchase totals =	$934.83		$1,005.4328	$1,005.43	$1,005.45	$1,005.40