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	$37.35	13.749%	$42.4853	$42.49	$42.50	$42.50
Purchase #2	$153.62	3.208%	$158.5481	$158.55	$158.55	$158.50
Purchase #3	$86.63	4.679%	$90.6834	$90.68	$90.70	$90.70
Purchase #4	$165.80	9.526%	$181.5941	$181.59	$181.60	$181.60
Purchase #5	$189.50	12.222%	$212.6607	$212.66	$212.65	$212.70
Purchase #6	$245.57	4.159%	$255.7833	$255.78	$255.80	$255.80
Purchase #7	$142.31	8.257%	$154.0605	$154.06	$154.05	$154.10
7 purchase totals =	$1,020.78		$1,095.8154	$1,095.81	$1,095.85	$1,095.90