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	$139.35	8.339%	$150.9704	$150.97	$150.95	$151.00
Purchase #2	$169.52	8.320%	$183.6241	$183.62	$183.60	$183.60
Purchase #3	$123.92	8.574%	$134.5449	$134.54	$134.55	$134.50
Purchase #4	$29.92	8.542%	$32.4758	$32.48	$32.50	$32.50
Purchase #5	$188.61	10.769%	$208.9214	$208.92	$208.90	$208.90
Purchase #6	$107.96	3.191%	$111.405	$111.41	$111.40	$111.40
Purchase #7	$102.58	3.636%	$106.3098	$106.31	$106.30	$106.30
7 purchase totals =	$861.86		$928.2514	$928.25	$928.20	$928.20