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	$40.77	13.351%	$46.2132	$46.21	$46.20	$46.20
Purchase #2	$83.65	13.724%	$95.1301	$95.13	$95.15	$95.10
Purchase #3	$171.73	10.768%	$190.2219	$190.22	$190.20	$190.20
Purchase #4	$170.97	9.164%	$186.6377	$186.64	$186.65	$186.60
Purchase #5	$61.65	5.669%	$65.1449	$65.14	$65.15	$65.10
Purchase #6	$92.89	7.842%	$100.1744	$100.17	$100.15	$100.20
Purchase #7	$139.36	4.492%	$145.6201	$145.62	$145.60	$145.60
7 purchase totals =	$761.02		$829.1423	$829.13	$829.10	$829.00