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	$101.54	12.218%	$113.9462	$113.95	$113.95	$113.90
Purchase #2	$143.27	5.601%	$151.2946	$151.29	$151.30	$151.30
Purchase #3	$212.37	3.633%	$220.0854	$220.09	$220.10	$220.10
Purchase #4	$116.29	3.839%	$120.7544	$120.75	$120.75	$120.80
Purchase #5	$51.50	5.737%	$54.4546	$54.45	$54.45	$54.50
Purchase #6	$202.82	3.678%	$210.2797	$210.28	$210.30	$210.30
Purchase #7	$83.75	8.160%	$90.584	$90.58	$90.60	$90.60
7 purchase totals =	$911.54		$961.3989	$961.39	$961.45	$961.50