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	$146.41	10.210%	$161.3585	$161.36	$161.35	$161.40
Purchase #2	$125.65	13.698%	$142.8615	$142.86	$142.85	$142.90
Purchase #3	$119.41	4.571%	$124.8682	$124.87	$124.85	$124.90
Purchase #4	$73.66	6.717%	$78.6077	$78.61	$78.60	$78.60
Purchase #5	$75.67	9.652%	$82.9737	$82.97	$82.95	$83.00
Purchase #6	$63.91	13.691%	$72.6599	$72.66	$72.65	$72.70
Purchase #7	$138.39	9.320%	$151.2879	$151.29	$151.30	$151.30
7 purchase totals =	$743.10		$814.6174	$814.62	$814.55	$814.80