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	$201.57	5.565%	$212.7874	$212.79	$212.80	$212.80
Purchase #2	$126.94	3.684%	$131.6165	$131.62	$131.60	$131.60
Purchase #3	$86.73	13.388%	$98.3414	$98.34	$98.35	$98.30
Purchase #4	$216.39	5.575%	$228.4537	$228.45	$228.45	$228.50
Purchase #5	$6.61	4.454%	$6.9044	$6.90	$6.90	$6.90
Purchase #6	$184.85	12.810%	$208.5293	$208.53	$208.55	$208.50
Purchase #7	$178.98	12.239%	$200.8854	$200.89	$200.90	$200.90
7 purchase totals =	$1,002.07		$1,087.5181	$1,087.52	$1,087.55	$1,087.50