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	$207.72	12.340%	$233.3526	$233.35	$233.35	$233.40
Purchase #2	$140.47	12.405%	$157.8953	$157.90	$157.90	$157.90
Purchase #3	$68.25	7.197%	$73.162	$73.16	$73.15	$73.20
Purchase #4	$141.31	13.748%	$160.7373	$160.74	$160.75	$160.70
Purchase #5	$131.47	6.389%	$139.8696	$139.87	$139.85	$139.90
Purchase #6	$246.61	3.809%	$256.0034	$256.00	$256.00	$256.00
Purchase #7	$93.86	10.262%	$103.4919	$103.49	$103.50	$103.50
7 purchase totals =	$1,029.69		$1,124.5121	$1,124.51	$1,124.50	$1,124.60