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	$178.38	7.412%	$191.6015	$191.60	$191.60	$191.60
Purchase #2	$73.54	13.388%	$83.3855	$83.39	$83.40	$83.40
Purchase #3	$231.94	9.776%	$254.6145	$254.61	$254.60	$254.60
Purchase #4	$143.67	8.585%	$156.0041	$156.00	$156.00	$156.00
Purchase #5	$206.75	10.444%	$228.343	$228.34	$228.35	$228.30
Purchase #6	$45.67	13.440%	$51.808	$51.81	$51.80	$51.80
Purchase #7	$196.94	4.335%	$205.4773	$205.48	$205.50	$205.50
7 purchase totals =	$1,076.89		$1,171.2339	$1,171.23	$1,171.25	$1,171.20