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	$154.57	8.302%	$167.4024	$167.40	$167.40	$167.40
Purchase #2	$200.90	11.504%	$224.0115	$224.01	$224.00	$224.00
Purchase #3	$110.60	11.747%	$123.5922	$123.59	$123.60	$123.60
Purchase #4	$10.34	13.665%	$11.753	$11.75	$11.75	$11.80
Purchase #5	$89.25	11.856%	$99.8315	$99.83	$99.85	$99.80
Purchase #6	$210.48	8.749%	$228.8949	$228.89	$228.90	$228.90
Purchase #7	$221.47	13.332%	$250.9964	$251.00	$251.00	$251.00
7 purchase totals =	$997.61		$1,106.4819	$1,106.47	$1,106.50	$1,106.50