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	$104.42	4.634%	$109.2588	$109.26	$109.25	$109.30
Purchase #2	$59.85	8.833%	$65.1366	$65.14	$65.15	$65.10
Purchase #3	$98.59	11.238%	$109.6695	$109.67	$109.65	$109.70
Purchase #4	$119.35	7.500%	$128.3013	$128.30	$128.30	$128.30
Purchase #5	$215.84	12.716%	$243.2862	$243.29	$243.30	$243.30
Purchase #6	$250.32	3.656%	$259.4717	$259.47	$259.45	$259.50
Purchase #7	$103.85	7.225%	$111.3532	$111.35	$111.35	$111.40
7 purchase totals =	$952.22		$1,026.4773	$1,026.48	$1,026.45	$1,026.60