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	$40.79	5.564%	$43.0596	$43.06	$43.05	$43.10
Purchase #2	$43.46	7.103%	$46.547	$46.55	$46.55	$46.50
Purchase #3	$79.96	3.609%	$82.8458	$82.85	$82.85	$82.80
Purchase #4	$116.93	8.250%	$126.5767	$126.58	$126.60	$126.60
Purchase #5	$13.56	7.358%	$14.5577	$14.56	$14.55	$14.60
Purchase #6	$172.41	11.137%	$191.6113	$191.61	$191.60	$191.60
Purchase #7	$182.66	5.625%	$192.9346	$192.93	$192.95	$192.90
7 purchase totals =	$649.77		$698.1327	$698.14	$698.15	$698.10