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	$147.82	11.769%	$165.2169	$165.22	$165.20	$165.20
Purchase #2	$104.35	4.587%	$109.1365	$109.14	$109.15	$109.10
Purchase #3	$110.69	9.447%	$121.1469	$121.15	$121.15	$121.10
Purchase #4	$200.87	9.255%	$219.4605	$219.46	$219.45	$219.50
Purchase #5	$82.55	8.806%	$89.8194	$89.82	$89.80	$89.80
Purchase #6	$162.93	13.569%	$185.038	$185.04	$185.05	$185.00
Purchase #7	$108.83	11.568%	$121.4195	$121.42	$121.40	$121.40
7 purchase totals =	$918.04		$1,011.2377	$1,011.25	$1,011.20	$1,011.10