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	$50.35	8.293%	$54.5255	$54.53	$54.55	$54.50
Purchase #2	$130.69	13.489%	$148.3188	$148.32	$148.30	$148.30
Purchase #3	$72.73	9.423%	$79.5833	$79.58	$79.60	$79.60
Purchase #4	$132.88	10.866%	$147.3187	$147.32	$147.30	$147.30
Purchase #5	$241.44	5.730%	$255.2745	$255.27	$255.25	$255.30
Purchase #6	$43.46	8.208%	$47.0272	$47.03	$47.05	$47.00
Purchase #7	$199.46	8.211%	$215.8377	$215.84	$215.85	$215.80
7 purchase totals =	$871.01		$947.8857	$947.89	$947.90	$947.80