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	$180.71	11.309%	$201.1465	$201.15	$201.15	$201.10
Purchase #2	$241.55	6.528%	$257.3184	$257.32	$257.30	$257.30
Purchase #3	$108.61	7.190%	$116.4191	$116.42	$116.40	$116.40
Purchase #4	$111.31	6.413%	$118.4483	$118.45	$118.45	$118.40
Purchase #5	$52.73	3.456%	$54.5523	$54.55	$54.55	$54.60
Purchase #6	$215.83	6.509%	$229.8784	$229.88	$229.90	$229.90
Purchase #7	$83.73	12.474%	$94.1745	$94.17	$94.15	$94.20
7 purchase totals =	$994.47		$1,071.9375	$1,071.94	$1,071.90	$1,071.90