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	$221.58	7.725%	$238.6971	$238.70	$238.70	$238.70
Purchase #2	$196.30	10.187%	$216.2971	$216.30	$216.30	$216.30
Purchase #3	$43.61	7.468%	$46.8668	$46.87	$46.85	$46.90
Purchase #4	$111.66	5.222%	$117.4909	$117.49	$117.50	$117.50
Purchase #5	$79.69	8.768%	$86.6772	$86.68	$86.70	$86.70
Purchase #6	$73.35	12.453%	$82.4843	$82.48	$82.50	$82.50
Purchase #7	$40.31	3.455%	$41.7027	$41.70	$41.70	$41.70
7 purchase totals =	$766.50		$830.2161	$830.22	$830.25	$830.30