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	$154.36	6.159%	$163.867	$163.87	$163.85	$163.90
Purchase #2	$6.64	13.186%	$7.5156	$7.52	$7.50	$7.50
Purchase #3	$73.92	6.467%	$78.7004	$78.70	$78.70	$78.70
Purchase #4	$169.89	11.695%	$189.7586	$189.76	$189.75	$189.80
Purchase #5	$24.58	11.759%	$27.4704	$27.47	$27.45	$27.50
Purchase #6	$13.93	5.563%	$14.7049	$14.70	$14.70	$14.70
Purchase #7	$174.34	6.496%	$185.6651	$185.67	$185.65	$185.70
7 purchase totals =	$617.66		$667.6820	$667.69	$667.60	$667.80