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	$202.36	8.426%	$219.4109	$219.41	$219.40	$219.40
Purchase #2	$32.57	9.694%	$35.7273	$35.73	$35.75	$35.70
Purchase #3	$198.83	13.452%	$225.5766	$225.58	$225.60	$225.60
Purchase #4	$59.94	11.174%	$66.6377	$66.64	$66.65	$66.60
Purchase #5	$190.76	10.649%	$211.074	$211.07	$211.05	$211.10
Purchase #6	$163.54	6.632%	$174.386	$174.39	$174.40	$174.40
Purchase #7	$81.50	5.340%	$85.8521	$85.85	$85.85	$85.90
7 purchase totals =	$929.50		$1,018.6646	$1,018.67	$1,018.70	$1,018.70