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	$92.83	9.471%	$101.6219	$101.62	$101.60	$101.60
Purchase #2	$158.42	8.859%	$172.4544	$172.45	$172.45	$172.50
Purchase #3	$133.70	8.479%	$145.0364	$145.04	$145.05	$145.00
Purchase #4	$54.30	8.709%	$59.029	$59.03	$59.05	$59.00
Purchase #5	$99.38	12.722%	$112.0231	$112.02	$112.00	$112.00
Purchase #6	$84.74	5.496%	$89.3973	$89.40	$89.40	$89.40
Purchase #7	$222.27	8.725%	$241.6631	$241.66	$241.65	$241.70
7 purchase totals =	$845.64		$921.2252	$921.22	$921.20	$921.20