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	$85.33	5.755%	$90.2407	$90.24	$90.25	$90.20
Purchase #2	$188.54	4.102%	$196.2739	$196.27	$196.25	$196.30
Purchase #3	$10.57	9.611%	$11.5859	$11.59	$11.60	$11.60
Purchase #4	$43.54	11.247%	$48.4369	$48.44	$48.45	$48.40
Purchase #5	$178.53	9.265%	$195.0708	$195.07	$195.05	$195.10
Purchase #6	$157.95	3.502%	$163.4814	$163.48	$163.50	$163.50
Purchase #7	$222.89	8.318%	$241.43	$241.43	$241.45	$241.40
7 purchase totals =	$887.35		$946.5196	$946.52	$946.55	$946.50