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	$188.92	5.818%	$199.9114	$199.91	$199.90	$199.90
Purchase #2	$102.40	10.841%	$113.5012	$113.50	$113.50	$113.50
Purchase #3	$219.40	9.186%	$239.5541	$239.55	$239.55	$239.60
Purchase #4	$25.52	8.815%	$27.7696	$27.77	$27.75	$27.80
Purchase #5	$100.40	4.329%	$104.7463	$104.75	$104.75	$104.70
Purchase #6	$86.54	12.604%	$97.4475	$97.45	$97.45	$97.40
Purchase #7	$99.71	9.709%	$109.3908	$109.39	$109.40	$109.40
7 purchase totals =	$822.89		$892.3209	$892.32	$892.30	$892.30