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	$138.84	6.488%	$147.8479	$147.85	$147.85	$147.80
Purchase #2	$106.72	10.724%	$118.1647	$118.16	$118.15	$118.20
Purchase #3	$151.88	8.679%	$165.0617	$165.06	$165.05	$165.10
Purchase #4	$143.27	13.188%	$162.1644	$162.16	$162.15	$162.20
Purchase #5	$99.35	12.377%	$111.6465	$111.65	$111.65	$111.60
Purchase #6	$102.81	13.402%	$116.5886	$116.59	$116.60	$116.60
Purchase #7	$213.30	11.286%	$237.373	$237.37	$237.35	$237.40
7 purchase totals =	$956.17		$1,058.8468	$1,058.84	$1,058.80	$1,058.90