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	$39.67	12.342%	$44.5661	$44.57	$44.55	$44.60
Purchase #2	$250.45	6.258%	$266.1232	$266.12	$266.10	$266.10
Purchase #3	$239.50	7.266%	$256.9021	$256.90	$256.90	$256.90
Purchase #4	$225.93	13.257%	$255.8815	$255.88	$255.90	$255.90
Purchase #5	$84.25	6.247%	$89.5131	$89.51	$89.50	$89.50
Purchase #6	$185.70	13.874%	$211.464	$211.46	$211.45	$211.50
Purchase #7	$90.75	13.862%	$103.3298	$103.33	$103.35	$103.30
7 purchase totals =	$1,116.25		$1,227.7798	$1,227.77	$1,227.75	$1,227.80