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	$28.61	13.247%	$32.4	$32.40	$32.40	$32.40
Purchase #2	$38.34	12.475%	$43.1229	$43.12	$43.10	$43.10
Purchase #3	$109.77	4.131%	$114.3046	$114.30	$114.30	$114.30
Purchase #4	$97.99	13.825%	$111.5371	$111.54	$111.55	$111.50
Purchase #5	$207.40	3.835%	$215.3538	$215.35	$215.35	$215.40
Purchase #6	$166.90	3.115%	$172.0989	$172.10	$172.10	$172.10
Purchase #7	$110.42	7.572%	$118.781	$118.78	$118.80	$118.80
7 purchase totals =	$759.43		$807.5983	$807.59	$807.60	$807.60