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	$12.51	4.420%	$13.0629	$13.06	$13.05	$13.10
Purchase #2	$24.61	11.536%	$27.449	$27.45	$27.45	$27.40
Purchase #3	$221.60	4.155%	$230.8075	$230.81	$230.80	$230.80
Purchase #4	$219.98	4.209%	$229.239	$229.24	$229.25	$229.20
Purchase #5	$84.87	7.418%	$91.1657	$91.17	$91.15	$91.20
Purchase #6	$175.83	5.689%	$185.833	$185.83	$185.85	$185.80
Purchase #7	$96.60	4.179%	$100.6369	$100.64	$100.65	$100.60
7 purchase totals =	$836.00		$878.1940	$878.20	$878.20	$878.10